Electromagnetic alignment and scanning apparatus

ABSTRACT

An apparatus capable of high accuracy position and motion control utilizes one or more linear commutated motors to move a guideless stage in one long linear direction and small yaw rotation in a plane. A carrier/follower holding a single voice coil motor (VCM) is controlled to approximately follow the stage in the direction of the long linear motion. The VCM provides an electromagnetic force to move the stage for small displacements in the plane in a linear direction perpendicular to the direction of the long linear motion to ensure proper alignment. One element of the linear commutated motors is mounted on a freely suspended drive assembly frame which is moved by a reaction force to maintain the center of gravity of the apparatus. Where one linear motor is utilized, yaw correction can be achieved utilizing two VCMs.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Invention

[0002] The present invention relates to a movable stage apparatuscapable of precise movement, and particularly relates to a stageapparatus movable in one linear direction capable of high accuracypositioning and high speed movement, which can be especially favorablyutilized in a microlithographic system. This invention also relates toan exposure apparatus that is used for the transfer of a mask patternonto a photosensitive substrate during a lithographic process tomanufacture, for example, a semiconductor element, a liquid crystaldisplay element, a thin film magnetic head, or the like.

[0003] 2. Description of Related Art

[0004] When a semiconductor element or the like is manufactured, aprojection exposure apparatus is used that transfers an image of apattern of a reticle, used as a mask, onto each shooting area on a wafer(or a glass plate or the like) on which a resist is coated, used as asubstrate, through a projection optical system. Conventionally, as aprojection exposure apparatus, a step-and-repeat type (batch exposuretype) projection exposure apparatus (stepper) has been widely used.However, a scanning exposure type projection exposure apparatus (ascanning type exposure apparatus), such as a step-and-scan type, whichperforms an exposure as a reticle and a wafer are synchronously scannedwith respect to a projection optical system, has attracted attention.

[0005] In a conventional exposure apparatus, a reticle stage, whichsupports and carries the reticle, which is the original pattern, and thewafer to which the pattern is to be transferred, and the driving part ofthe wafer stage are fixed to a structural body that supports aprojection optical system. The vicinity of the center of gravity of theprojection optical system is also fixed to the structural body.Additionally, in order to position a wafer stage with high accuracy, theposition of the wafer stage is measured by a laser interferometer, and amoving mirror for the laser interferometer is fixed to the wafer stage.

[0006] Furthermore, in order to carry a wafer to a wafer holder on thewafer stage, a wafer carrier arm that takes out a wafer from a wafercassette and carries it to the wafer holder, and a wafer carrier armthat carries the wafer from the wafer holder to the wafer cassette, areindependently provided. When the wafer is carried in, the wafer that hasbeen carried by the wafer carrier arm is temporarily fixed to andsupported by a special support member that can be freely raised andlowered and that is provided on the wafer holder. Thereafter, thecarrier arm is withdrawn, the support member is lowered, and the waferis disposed on the wafer holder. After this, the wafer is vacuumabsorbed to the top of the wafer holder. When the wafer is carried outfrom the exposure device, the opposite operation is performed.

[0007] As described above, in the conventional exposure apparatus, thedriving part of the wafer stage or the like and the projection opticalsystem are fixed to the same structural body. Thus, the vibrationgenerated by the driving reaction of the stage is transmitted to thestructural body, and the vibration is also transmitted to the projectionoptical system. Furthermore, all the mechanical structures weremechanically resonate to a vibration of a predetermined frequency, sothere are disadvantages such that deformation of the structural body andthe resonance phenomenon occurred, and position shifting of a transferpattern image and deterioration of contrast occurred when this type ofvibration is transmitted to the structural body.

[0008] Furthermore, because the wafer stage moves over a long distancefrom the carrier arm for carrying in and out of the wafer to theexposure position, it is necessary to provide an extremely long movingmirror for the laser interferometer. Because of this, the weight of thewafer stage becomes relatively heavy and the driving reaction becomeslarge because a heavy motor with a large driving force is needed.Furthermore, in order to improve throughput, when the moving speed andacceleration of the stage needs to be increased, the driving reactionbecomes even larger. In addition, as the weight and acceleration of thestage increase, the heating amount of the motor increases, and there isa disadvantage such that measurement stability or the like of the laserinterferometer deteriorates.

[0009] Furthermore, in the case of carrying the wafer into and out ofthe exposure apparatus, the wafer is temporarily fixed and supported onthe top of a special support member, so carrying in and out of the waferconsumes time. This causes deterioration of throughput. Additionally, asone example, because giving and receiving of the wafer is performedbetween the carrier arms, the probability of the wafer beingcontaminated is high, and the probability of having an operation errorwhen the wafer was given and received is high. Furthermore, the numberof carrier arms is a major point governing the size of the carrier unit,so the carrier path becomes long when giving and receiving of the waferis performed between the carrier arms on the carrier path. Additionally,a floor area (foot print) that is needed for the exposure apparatus alsobecomes large.

[0010] In wafer steppers, the alignment of an exposure field to thereticle being imaged affects the success of the circuit of that field.In a scanning exposure system, the reticle and wafer are movedsimultaneously and scanned across one another during the exposuresequence.

[0011] To attain high accuracy, the stage should be isolated frommechanical disturbances. This is achieved by employing electromagneticforces to position and move the stage. It should also have high controlbandwidth, which requires that the stage be a light structure with nomoving parts. Furthermore, the stage should be free from excessive heatgeneration which might cause interferometer interference or mechanicalchanges that compromise alignment accuracy.

[0012] Commutatorless electromagnetic alignment apparatus such as theones disclosed in U.S. Pat. Nos. 4,506,204, 4,506,205 and 4,507,597 arenot feasible because they require the manufacture of large magnet andcoil assemblies that are not commercially available. The weight of thestage and the heat generated also render these designs inappropriate forhigh accuracy applications.

[0013] An improvement over these commutatorless apparatus was disclosedin U.S. Pat. No. 4,592,858, which employs a conventional XY mechanicallyguided sub-stage to provide the large displacement motion in a plane,thereby eliminating the need for large magnet and coil assemblies. Theelectromagnetic means mounted on the sub-stage isolates the stage frommechanical disturbances. Nevertheless, the combined weight of thesub-stage and stage still results in low control bandwidth, and the heatgenerated by the electromagnetic elements supporting the stage is stillsubstantial.

[0014] Even though the current apparatus using commutatedelectromagnetic means is a significant improvement over priorcommutatorless apparatus, the problems of low control bandwidth andinterferometer interference persist. In such an apparatus, a sub-stageis moved magnetically in one linear direction and the commutatedelectromagnetic means mounted on the sub-stage in turn moves the stagein the normal direction. The sub-stage is heavy because it carries themagnet tracks to move the stage. Moreover, heat dissipation on the stagecompromises interferometer accuracy.

[0015] It is also well known to move a movable member (stage) in onelong linear direction (e.g. more than 10 cm) by using two of the linearmotors in parallel where coil and magnet are combined. In this case, thestage is guided by some sort of a linear guiding member and driven inone linear direction by a linear motor installed parallel to the guidingmember. When driving the stage only to the extent of extremely smallstroke, the guideless structure based on the combination of severalelectromagnetic actuators, as disclosed in the prior art mentionedbefore, can be adopted. However, in order to move the guideless stage bya long distance in one linear direction, a specially structuredelectromagnetic actuator as in the prior art becomes necessary, causingthe size of the apparatus to become larger, and as a result, generatinga problem of consuming more electricity.

SUMMARY OF THE INVENTION

[0016] It is an object of the present invention to make it possible fora guideless stage to move with a long linear motion usingelectromagnetic force, and to provide a light weight apparatus in whichlow inertia and high response are achieved.

[0017] It is another object of the present invention to provide aguideless stage apparatus using commercially available regular linearmotors as electromagnetic actuators for one linear direction motion.

[0018] It is another object of the present invention to provide aguideless stage apparatus capable of active and precise position controlfor small displacements without any contact in the direction orthogonalto the long linear motion direction.

[0019] It is another object of the present invention to provide acompletely non-contact stage apparatus by providing a movable member(stage body) that moves in one linear direction and a second movablemember that moves sequentially in the same direction, constantly keepinga certain space therebetween, and providing the electromagnetic force(action and reaction forces) in the direction orthogonal to the lineardirection between this second movable member and the stage body.

[0020] It is another object of the present invention to provide anon-contact stage apparatus capable of preventing the positioning andrunning accuracy from deteriorating by changing tension of variouscables and tubes to be connected to the non-contact stage body thatmoves as it supports an object.

[0021] It is another object of the present invention to provide anon-contact apparatus that is short in its height, by arranging thefirst movable member and the second movable member in parallel, whichmove in the opposite linear direction to one another.

[0022] It is another object of the present invention to provide anapparatus that is structured so as not to change the location of thecenter of gravity of the entire apparatus even when the non-contactstage body moves in one linear direction.

[0023] Another object of this invention is to provide an exposureapparatus that can perform an exposure with high accuracy by reducingthe effects of vibration on a projection optical system or the like thatoccurs when the wafer stage or the like is driven.

[0024] Another object of this invention is to provide an exposureapparatus that suppresses the amount of heat generated by the drivingpart of the wafer stage, to perform positioning of the driving part ofthe wafer stage with high accuracy, and to maintain the measurementstability of a position measurement device or the like.

[0025] Another object of this invention is to provide an exposureapparatus with high throughput that can carry a wafer to an exposureapparatus without temporarily fixing the wafer, and without giving andreceiving of the wafer between wafer carrier arms.

[0026] In order to achieve the above and other objects, embodiments ofthe present invention may be constructed as follows.

[0027] An apparatus that is capable of high accuracy position and motioncontrol utilizes linear commutated motors to move a guideless stage inone long linear direction and to create small yaw rotation in a plane. Acarrier/follower holding a single voice coil motor (VCM) is controlledto approximately follow the stage in the direction of the long linearmotion. The VCM provides an electromagnetic force to move the stage forsmall displacements in the plane in a linear direction perpendicular tothe direction of the long linear motion to ensure proper alignment. Thisfollower design eliminates the problem of cable drag for the stage sincethe cables connected to the stage follow the stage via thecarrier/follower. Cables connecting the carrier/follower to externaldevices will have a certain amount of drag, but the stage is free fromsuch disturbances because the VCM on the carrier/follower acts as abuffer by preventing the transmission of mechanical disturbances to thestage.

[0028] According to one aspect of the invention, the linear commutatedmotors are located on opposite sides of the stage and are mounted on adriving frame. Each linear commutated motor includes a coil member and amagnetic member, one of which is mounted on one of the opposed sides ofthe stage, and the other of which is mounted on the driving frame. Bothmotors drive in the same direction. By driving the motors slightlydifferent amounts, small yaw rotation of the stage is produced.

[0029] In accordance with another aspect of the present invention, amoving counter-weight is provided to preserve the location of the centerof gravity of the stage system during any stage motion by using theconservation of momentum principle. In an embodiment of the presentinvention, the drive frame carrying one member of each of the linearmotors is suspended above the base structure, and when the driveassembly applies an action force to the stage to move the stage in onedirection over the base structure, the driving frame moves in theopposite direction in response to the reaction force to substantiallymaintain the center of gravity of the apparatus. This apparatusessentially eliminates any reaction forces between the stage system andthe base structure on which the stage system is mounted, therebyfacilitating high acceleration while minimizing vibrational effects onthe system.

[0030] By restricting the stage motion to the three specified degrees offreedom, the apparatus is simple. By using electromagnetic componentsthat are commercially available, the apparatus design is easilyadaptable to changes in the size of the stage. This high accuracypositioning apparatus is ideally suited for use as a reticle scanner ina scanning exposure system by providing smooth and precise scanningmotion in one linear direction and ensuring accurate alignment bycontrolling small displacement motion perpendicular to the scanningdirection and small yaw rotation in the scanning plane.

[0031] An exposure apparatus according to another aspect of thisinvention includes a projection optical system support member thatsupports a projection optical system, so that the projection opticalsystem rotates within a specified area, taking a reference point as acenter. Therefore, even if vibration from a substrate stage and a maskstage is transmitted to the projection optical system, the positionrelationship between the object plane (mask) and the image plane(substrate) is not shifted. Thus, it is possible to prevent positionshifting of the pattern to be transferred, and highly accurate exposurecan be performed.

[0032] Furthermore, a mask stage that moves a mask, a structural bodythat supports this mask stage and the projection optical system, and asubstrate stage that moves a substrate are provided. The projectionoptical system support part (the structural body) has at least threeflexible support members extending from the structural body, and theextending lines of each support member cross at the reference point. Inthis case, even if vibration is transmitted to the projection opticalsystem, the projection optical system is minutely rotated taking thereference point as a center. Therefore, it is possible to preventposition shifting of the pattern to be transferred to the substrate.Furthermore, the support members are flexible, so the minute vibrationcan be reduced and the deterioration of contrast of a pattern to beformed can be prevented.

[0033] An exposure apparatus according to another aspect of thisinvention controls the mask base so that the mask base moves at aspecified speed in a direction opposite to the moving direction of themask stage. This reduces the effects to the structural body of thedriving reaction of the mask stage. Additionally, the excitation ofmechanical resonance is controlled, and the vibration transmitted to thestructural body and the projection optical system can be reduced.Therefore, exposure with a high accuracy can be performed.

[0034] In an exposure apparatus according to another aspect of thisinvention, by having an elastic member at both ends of a guide axis,when the substrate table performs constant velocity reciprocation on theguide axis, the kinetic energy of the substrate table is converted topotential energy and is stored in the elastic members. Therefore, theenergy to be consumed when the substrate table is reciprocated atconstant velocity is mainly only the energy to be consumed in theviscosity resistance of the substrate table with respect to air. Theonly heat generated is the heat from when the elastic members aredeformed. Therefore, it is possible to control the heating amount of thedriving part when the substrate table moves at constant velocity.

[0035] Furthermore, when the elastic member has first magnetic membersdisposed at both ends of the guide axis and second magnetic membersdisposed corresponding to the first magnetic members, by the attractionof the first and second magnetic members, when the substrate table isstill-positioned at an end of the guide axis, it is possible to reducethe thrust of the driving part of the substrate table required to opposethe resistance of the elastic member. Thus, the heating amount of thedriving part can be controlled when the substrate table isstill-positioned.

[0036] In an exposure apparatus according to another aspect of thisinvention, by controlling the length of the support legs that can befreely extended and retracted in the support direction, the tilt angleof the substrate table and its position in the height direction can becontrolled, and highly accurate exposure can be performed as the surfaceof the substrate is aligned within the image plane.

[0037] Furthermore, when the mask and the substrate are synchronouslyand moved during exposure, the tilt angle of the scanning surface of thesubstrate stage of the structural body in the scanning direction, thetilt angle in the non-scanning direction, and the height are detected.When the support legs that can be freely extended and retracted arecontrolled based upon the detection result, highly accurate scanningexposure can be performed as the surface of the substrate is alignedwithin the image plane.

[0038] Furthermore, when the rotation angle of the substrate stage aboutthe optical axis of the projection optical system and the positionshifting amount are detected, and the position of the mask stage or thesubstrate stage is controlled based upon this detection result, thepositioning between the surface of the substrate and the image plane canbe performed with high accuracy.

[0039] In an exposure apparatus according to another aspect of thisinvention, a visco-elastic body exists between the support member andthe structural body, so it is possible to reduce the vibration from thefloor on which the exposure device is disposed. Therefore, exposure canbe performed with high accuracy.

[0040] In an exposure apparatus according to another aspect of thisinvention, at least one groove is provided in the substrate table, and asubstrate can be disposed on the substrate table without the substratecarrier arms contacting the substrate table. That is, there is anadvantage such that the substrate can be carried into and out from theexposure device, without temporarily fixing and supporting the substrateon the substrate table, and throughput can be improved.

[0041] Furthermore, when the substrate carrier mechanism has at leasttwo substrate carrier arms and substrate storage case support members,the substrate carrier arms can be freely moved in the three directionssuch as a rotational direction about the optical axis of the projectionoptical system, the horizontal direction, and the vertical direction,and the substrate storage case support member can be freely moved in thevertical direction, there are advantages such that the substrate stagecan be moved below the substrate carrying-out arms or the substratecarrying-in arms, the substrate can be carried to the exposure devicewithout transferring the substrate between the substrate carrier arms,and the probability of problems occurring during the carrying and theprobability of foreign objects attaching to the wafer can be reduced.

[0042] Other aspects and features and advantages of the presentinvention will become more apparent upon a review of the followingspecification taken in conjunction with the accompanying drawingswherein similar characters of reference indicate similar elements ineach of the several views.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043]FIG. 1 is a schematic perspective view of an apparatus inaccordance with an embodiment of the present invention.

[0044]FIG. 2 is a top plan view of the apparatus shown in FIG. 1.

[0045]FIG. 3 is an end elevational view of the structure shown in FIG. 2taken along line 3-3′ in the direction of the arrows.

[0046]FIG. 4A is an enlarged perspective, partially exploded viewshowing the carrier/follower structure of FIG. 1 and exploded from thepositioning guide.

[0047]FIG. 4B is an enlarged horizontal sectional view of a portion ofthe structure shown in FIG. 5 taken along line 4B in the direction ofthe arrow.

[0048]FIG. 4C is an enlarged elevational sectional view of a portion ofthe structure shown in FIG. 2 taken along line 4C in the direction ofthe arrow but with the voice coil motor removed.

[0049]FIG. 5 is an elevational sectional view of a portion of thestructure shown in FIG. 2 taken along line 5-5′ in the direction of thearrows.

[0050]FIG. 6 is a block diagram schematically illustrating the sensingand control systems for controlling the position of the stage.

[0051]FIG. 7 is a plan view, similar to FIG. 2, illustrating a preferredembodiment of the present invention.

[0052]FIG. 8 is an elevational sectional view of the structure shown inFIG. 7 taken along line 8-8′ in the direction of the arrows.

[0053]FIGS. 9 and 10 are simplified schematic views similar to FIGS. 7and 8 and illustrating still another embodiment of the presentinvention.

[0054]FIG. 11 is a perspective view showing a schematic structure of aprojection exposure apparatus according to an embodiment of thisinvention.

[0055]FIG. 12 is a cross-sectional view taken through a part showing amethod of supporting the projection optical system of FIG. 11.

[0056]FIG. 13A is a plan view showing the wafer stage of FIG. 11. FIG.13B is a cross-sectional view of FIG. 13A along line B-B. FIG. 13C is afront view omitting part of FIG. 13A. FIG. 13D is a cross-sectional viewof FIG. 13A along line D-D.

[0057]FIG. 14 is a block diagram showing a structure of a controllerthat controls a wafer table and a carrier.

[0058] FIGS. 15A-C are schematic diagrams that accompany an operationexplanation of a guide shaft and a guide member of the wafer table ofFIGS. 13A-C.

[0059]FIG. 16A is a diagram showing the speed of the wafer table whenthe moving speed of the wafer table is shifted to a constant speed on aguide axis without an elastic body. FIG. 16B is a diagram showing thrustof linear motors.

[0060]FIG. 17A is a diagram showing a speed curve of a wafer table thatis calculated assuming the case where an ideal wafer table withoutvibration is accelerated to a constant speed on a guide axis withsprings. FIG. 17B is a diagram showing thrust of linear motors which iscalculated assuming the case where a wafer table with vibration iscontrolled taking the speed curve of FIG. 17A as a speed governingvalue.

[0061]FIG. 18A is a diagram showing the speed when a wafer table isaccelerated to a constant speed using a guide axis with springs, takingthe speed curve of FIG. 17A as a speed governing value. FIG. 18B is adiagram showing thrust of a wafer table at that time and the thrustgenerated by linear motors.

[0062]FIG. 19A is a diagram showing a speed curve when a wafer table isaccelerated to a constant speed when a guide axis with springs in whicha spring constant is the optimum value is used. FIG. 19B is a diagramshowing thrust of the wafer table.

[0063]FIG. 20 is a diagram showing the resistance of the springs at theends of a guide axis with springs.

[0064] FIGS. 21A-C are schematic diagrams that accompany the explanationof the operation of the guide member and the guide shaft when a magneticmember is further provided.

[0065]FIG. 22A is a diagram showing speed that is calculated assumingthe case where an ideal wafer table without vibration is accelerated toa constant speed on a guide axis provided with springs, steel plates,and magnets. FIG. 22B is a diagram showing thrust of linear motorscalculated assuming the case where a wafer table with vibration iscontrolled taking the speed curve of FIG. 22A as a speed governingvalue.

[0066]FIG. 23A is a diagram showing the speed curve when a wafer tableon a guide axis with steel plates and magnets is accelerated to aconstant speed, taking the speed curve of FIG. 22A as a speed governingvalue. FIG. 23B is a diagram showing thrust of the wafer table at thattime, and the thrust of linear motors.

[0067]FIG. 24 is a diagram showing the resultant force between theresistance of the spring and the attraction between the magnet and thesteel plate at an end of the guide axis to which the steel plate and themagnet are fixed.

[0068]FIG. 25A is a schematic diagram showing a support leg thatsupports a wafer table, and the vicinity thereof, by enlargement. FIG.25B is a side view of FIG. 25A.

[0069]FIG. 26 is a block diagram showing a structure of a controllerthat controls a reticle stage, a wafer stage, and a wafer base.

[0070] FIGS. 27A-B are diagrams explaining the operation of the waferstage when a wafer is carried into or out from an exposure device.

[0071] FIGS. 28A-B are diagrams explaining the operation of a wafercarrier arm when an already-exposed wafer is carried out from anexposure device.

[0072] FIGS. 29A-B are diagrams explaining the operation of a wafercarrier arm when a non-exposed wafer is carried into an exposure device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0073] While the present invention has applicability generally toelectromagnetic alignment system, the preferred embodiments involve ascanning apparatus for a reticle stage as illustrated in FIGS. 1-6.

[0074] Referring now to the drawings, the positioning apparatus 10 ofthe present invention includes a base structure 12 above which a reticlestage 14 is suspended and moved as desired, a reticle stage positiontracking laser interferometer system 15, a position sensor 13 and aposition control system 16 operating from a CPU 16′ (see FIG. 6).

[0075] An elongate positioning guide 17 is mounted on the base 12, andsupport brackets 18 (two brackets in the illustrated embodiment) aremovably supported on the guide 17 such as by air bearings 20. Thesupport brackets 18 are connected to a driving assembly 22 in the formof a magnetic track assembly or driving frame for driving the reticlestage 14 in the X direction and small yaw rotation. The driving frameincludes a pair of parallel spaced apart magnetic track arms 24 and 26which are connected together to form an open rectangle by cross arms 28and 30. In the preferred embodiment, the driving frame 22 is movablysupported on the base structure 12 such as by air bearings 32 so thatthe frame is free to move on the base structure in a direction alignedwith the longitudinal axis of the guide 17, the principal direction inwhich the scanning motion of the reticle stage is desired. As usedherein “one direction” or a “first direction” applies to movement of theframe 22 or the reticle stage 14 either forward or backward in the Xdirection along a line aligned with the longitudinal axis of the guide17.

[0076] Referring now to FIGS. 1 and 3 to explain further in detail, theelongate guiding member 17 in the X direction has front and rear guidingsurfaces 17A and 17B, which are almost perpendicular to the surface 12Aof the base structure 12. The front guiding surface 17A is against therectangular driving frame 22 and guides the air bearing 20 which isfixed to the inner side of the support bracket 18. A support bracket 18is mounted on each end of the upper surface of the arm 24, which isparallel to the guiding member 17 of the driving frame 22. Furthermore,each support bracket 18 is formed in a hook shape so as to straddle theguiding member 17 in the Y direction, and with the free end against therear guiding surface 17B of the rear side of the guiding member 17. Theair bearing 20′ is fixed inside the free end of the support brackets 18and against the rear guiding surface 17B. Therefore, each of the supportbrackets 18 is constrained in its displacement in the Y direction by theguiding member 17 and air bearings 20 and 20′ and is able to move onlyin the X direction.

[0077] Now according to the first embodiment of the present invention,the air bearings 32, which are fixed to the bottom surfaces of the fourrectangular parts of the driving frame 22, make an air layer leaving aconstant (several μm) between the pad surface and the surface 12A of thebase structure 12. The driving frame is buoyed up from the surface 12Aand supported perpendicularly (in the Z direction) by the air layer. Itwill be explained in detail later, but in FIG. 1, the carrier/follower60 shown positioned above the upper part of the elongate arm 24 ispositioned laterally in the Y direction by air bearings 66A and 66Bsupported by a bracket 62 against opposite surfaces 17A and 17B ofguiding member 17 and vertically in the Z direction by air bearings 66above the surface 12A of the base structure 12. Thus, thecarrier/follower 60 is positioned so as not to contact any part of thedriving frame 22. Accordingly, the driving frame 22 moves only in onelinear X direction, guided above the base surface 12A and laterally bythe guiding member 17.

[0078] Referring now to both FIG. 1 and FIG. 2, the structure of thereticle stage 14 and the driving frame 22 will be explained. The reticlestage 14 includes a main body 42 on which the reticle 44 is positionedabove an opening 46. The reticle body 42 includes a pair of opposedsides 42A and 42 b and is positioned or suspended above the basestructure 12 such as by air bearings 48. A plurality of interferometermirrors 50 are provided on the main body 42 of the reticle stage 14 foroperation with the laser interferometer position sensing system 15 (seeFIG. 6) for determining the exact position of the reticle stage which isfed to the position control system 16 in order to direct the appropriatedrive signals for moving the reticle stage 14 as desired.

[0079] Primary movement of the reticle stage 14 is accomplished withfirst electromagnetic drive assembly or means in the form of separatedrive assemblies 52A and 52B (FIG. 2) on each of the opposed sides 42Aand 42B, respectively. The drive assemblies 52A and 52B include drivecoils 54A and 54B fixedly mounted on the reticle stage 14 at the sides42A and 42B, respectively, for cooperating with magnet tracks 56A and56B on the magnet track arms 24 and 26, respectively, of the drive frame22. While in the preferred embodiment of the invention the magnet coilsare mounted on the reticle stage and the magnets are mounted on thedrive frame 22, the positions of these elements of the electromagneticdrive assembly 52 could be reversed.

[0080] Here, the structure of the reticle stage 14 will be explainedfurther in detail. As shown in FIG. 1, the stage body 42 is installed sothat it is free to move in the Y direction in the rectangular spaceinside the driving frame 22. The air bearing 48 fixed under each of thefour corners of the stage body 42 makes an extremely small air gapbetween the pad surface and the base surface 12A, and buoys up andsupports the entire stage 14 from the surface 12A. These air bearings 48should preferably be pre-loaded types with a recess for vacuumattraction to the surface 12A.

[0081] As shown in FIG. 2, a rectangular opening 46 in the center of thestage body 42 is provided so that the projected image of the patternformed on the reticle 44 can pass therethrough. In order for theprojected image via the rectangular opening 46 to pass through theprojection optical system PL (see FIG. 5) which is installed below therectangular opening, there is another opening 12B provided at the centerpart of the base structure 12. The reticle 44 is loaded on the topsurface of the stage body by clamping members 42C, which areprotrusively placed at four points around the rectangular opening 46,and clamped by vacuum pressure.

[0082] The interferometer mirror 50Y, which is fixed near the side 42Bof the stage body 42 near the arm 26, has a vertical elongate reflectingsurface in the X direction which length is somewhat longer than themovable stroke of the stage 14 in the X direction, and the laser beamLBY from the Y-axis interferometer is incident perpendicularly on thereflecting surface. In FIG. 2, the laser beam LBY is bent at a rightangle by the mirror 12D, which is fixed on the side of the basestructure 12.

[0083] Referring now to FIG. 3 as a partial cross-sectional drawing ofthe view along line 3-3′ in FIG. 2, the laser beam LBY which is incidenton the reflecting surface of the interferometer mirror 50Y is placed soas to be on the same plane as the bottom surface (the surface where thepattern is formed) of the reticle 44 which is mounted on the clampingmember 42C. Furthermore, in FIG. 3, the air bearing 20 on the end sideof the support brackets 18 against the guiding surface 17B of theguiding member 17 is also shown.

[0084] Referring once again to FIGS. 1 and 2, the laser beam LBX1 fromthe X1-axis interferometer is incident and reflected on theinterferometer mirror 50X1, and the laser beam LBX2 from the X2-axisinterferometer is incident and reflected on the interferometer mirror50X2. These two mirrors 50X1 and 50X2 are structured as corner tube typemirrors, and even when the stage 14 is in yaw rotation, they alwaysmaintain the incident axis and reflecting axis of the laser beamsparallel within the XY plane. Furthermore, the block 12C in FIG. 2 is anoptical block, such as a prism, to orient the laser beams LBX1 and LBX2to each of the mirrors 50X1 and 50X2, and is fixed to a part of the basestructure 12. The corresponding block for the laser beam LBY is notshown.

[0085] In FIG. 2, the distance BL in the Y direction between each of thecenter lines of the two laser beams LBX1 and LBX2 is the length of thebase line used to calculate the amount of yaw rotation. Accordingly, thevalue of the difference between the measured value ΔX1 in the Xdirection of the X1-axis interferometer and the measured value ΔX2 inthe X direction of the X2-axis interferometer divided by the base linelength BL is the approximate amount of yaw rotation in an extremelysmall range. Also, half the value of the sum of ΔX1 and ΔX2 representsthe X coordinate position of the entire stage 14. These calculations areperformed by a high speed digital processor in the position controlsystem 16 shown in FIG. 6.

[0086] Furthermore, the center lines of each of the laser beams LBX1 andLBX2 are set on the same surface where the pattern is formed on thereticle 44. The extension of the line GX, which is shown in FIG. 2 anddivides in half the space between each of the center lines of laserbeams LBX1 and LBX2, and the extension of the laser beam LBY intersectwithin the same surface where the pattern is formed. Additionally, theoptical axis AX (see FIGS. 1 and 5) also crosses at this intersection asshown in FIG. 1. In FIG. 1, a slit shaped illumination field ILS whichincludes the optical axis AX is shown over the reticle 44, and thepattern image of the reticle 44 is scanned and exposed onto thephotosensitive substrate via the projection optical system PL.

[0087] Furthermore, there are two rectangular blocks 90A and 90B fixedon the side 42A of the stage body 42 in FIGS. 1 and 2. These blocks 90Aand 90B are to receive the driving force in the Y direction from thesecond electromagnetic actuator 70 which is mounted on thecarrier/follower 60. Details will be explained below.

[0088] The driving coils 54A and 54B which are fixed on the both sidesof the stage body 42 are formed flat parallel to the XY plane, and passthrough the magnetic flux space in the slot which extends in the Xdirection of the magnetic tracks 56A and 56B without any contact. Theassembly of the driving coil 54 and the magnetic track 56 used in thepresent embodiment is a commercially easily accessible linear motor forgeneral purposes, and it could be either with or without a commutator.

[0089] Here, considering the actual design, the moving stroke of thereticle stage 14 is mostly determined by the size of the reticle 44 (theamount of movement required at the time of scanning for exposure and theamount of movement required at the time of removal of the reticle fromthe illumination optical system to change the reticle). In the case ofthe present embodiment, when a 6-inch reticle is used, the moving strokeis about 30 cm.

[0090] As mentioned before, the driving frame 22 and the stage 14 areindependently buoyed up and supported on the base surface 12A, and atthe same time, magnetic action and reaction forces are applied to oneanother in the X direction only by the linear motor 52. Because of that,the law of the conservation of momentum is seen between the drivingframe 22 and the stage 14.

[0091] Now, suppose the weight of the entire reticle stage 14 is aboutone fifth of the entire weight of the frame 22 which includes thesupport brackets 18. Then, the forward movement of 30 cm of the stage 14in the X direction makes the driving frame 22 move by 6 cm backwards inthe X direction. This means that the location of the center of gravityof the apparatus on the base structure 12 is essentially fixed in the Xdirection. In the Y direction, there is no movement of any heavy object.Therefore, the change in the location of the center of gravity in the Ydirection is also relatively fixed.

[0092] The stage 14 can be moved in the X direction as described above,but the moving coils (54A, 54B) and the stators (56A, 56B) of the linearmotors 52 will interfere with each other (collide) in the Y directionwithout an X direction actuator. Therefore, the carrier/follower 60 andthe second electromagnetic actuator 70 are provided to control the stage14 in the Y direction. Their structures will be explained with referenceto FIGS. 1, 2, 3 and 5.

[0093] As shown in FIG. 1, the carrier/follower 60 is movably installedin the Y direction via the hook-like support bracket 62 which straddlesover the guiding member 17. Furthermore as evident from FIG. 2, thecarrier/follower 60 is placed above the arm 24, so as to maintain acertain space between the stage 14 (the body 42) and the arm 24,respectively. One end 60E of the carrier/follower 60, is substantiallyprotruding inward (toward the stage body 42) over the arm 24. Insidethis end part 60E is fixed a driving coil 68 (FIGS. 4A and 6) (havingthe same shape as the coil 54) which enters a slot space of the magnetictrack 56A.

[0094] Furthermore, the bracket 62 supported by air bearing 66A (seeFIGS. 2, 3, 4A and 5) against the guiding surface 17A of the guidingmember 17 is fixed in the space between the guiding member 17 of thecarrier/follower 60 and the arm 24. The air bearing 66 that buoys up andsupports the carrier/follower 60 on the base surface 12A is also shownin FIG. 3.

[0095] The air bearing 66B against the guiding surface 17B of theguiding member 17 is also fixed to the free end of support bracket 62 onthe other side of the hook from air bearing 66A with guiding member 17therebetween.

[0096] Now, as evident from FIG. 5, the carrier/follower 60 is arrangedso as to keep certain spaces with respect to both the magnetic track 56Aand the stage body 42 in the Y and Z directions, respectively. Shown inFIG. 5 are the projection optical system PL and column rod CB to supportthe base structure 12 above the projection optical system PL. Such anarrangement is typical for a projection aligner, and unnecessary shiftof the center of gravity of the structures above the base structure 12would cause a lateral shift (mechanical distortion) between the columnrod CB and the projection optical system PL, and thus result in adeflection of the image on the photosensitive substrate at the time ofexposure. Hence, the merit of the device as in the present embodimentwhere the motion of the stage 14 does not shift the center of gravityabove the base structure 12 is substantial.

[0097] Furthermore referring now to FIG. 4A, the structure of thecarrier/follower 60 will be explained. In FIG. 4A, the carrier/follower60 is disassembled into two parts, 60A and 60B, for the sake offacilitating one's understanding. As evident from FIG. 4A, the drivingcoil 68 that moves the carrier/follower 60 itself in the X direction isfixed at the lower part of the end 60E of the carrier/follower 60.Furthermore, the air bearing 66C is placed against the base structure12A on the bottom surface of the end 60E and helps to buoy up thecarrier/follower 60.

[0098] Hence the carrier/follower 60 is supported in the Z directionwith three points—the two air bearings 66 and one air bearing 66C—and isconstrained in the Y direction for movement in the X direction by airbearings 66A and 66B. What is important in this structure is that thesecond electromagnetic actuator 70 is arranged back to back with thesupport bracket 62 so that when the actuator generates the driving forcein the Y direction, reaction forces in the Y direction between the stage14 and the carrier/follower 60 actively act upon the air bearings 66Aand 66B which are fixed inside the support bracket 62. In other words,arranging the actuator 70 and the air bearings 66A, 66B on the lineparallel to the Y-axis in the XY plane helps prevent the generation ofunwanted stress, which might deform the carrier/follower 60 mechanicallywhen the actuator 70 is in operation. Conversely, it means that it ispossible to reduce the weight of the carrier/follower 60.

[0099] As evident from FIGS. 2, 4A and 4C described above, the magnetictrack 56A in the arm 24 of the driving frame 22 provides magnetic fluxfor the driving coil 54A on the stage body 42 side, and concurrentlyprovides magnetic flux for the driving coil 68 for the carrier/follower60. As for the air bearings 66A, 66B and 66C, a vacuum pre-loaded typeis preferable, since the carrier/follower 60 is light. Besides thevacuum pre-loaded type, a magnetic pre-loaded type is also acceptable.

[0100] Next with reference to FIGS. 3, 4B and 5, the second actuatormounted on the carrier/follower 60 will be explained. A secondelectromagnetic drive assembly in the form of a voice coil motor 70 ismade up of a voice coil 74 attached to the main body 42 of the reticlestage 14 and a magnet 72 attached to the carrier/follower 60 to move thestage 14 for small displacements in the Y direction in the plane oftravel of the stage 14 orthogonal to the X direction long linear motionproduced by the driving assembly 22. The positions of the coil 74 andmagnet 72 could be reversed. A schematic structure of the voice coilmotor (VCM) 70 is as shown in FIGS. 3 and 5, and the detailed structureis shown in FIG. 4B. FIG. 4B is a cross-sectional view of the VCM 70sectioned at the horizontal plane shown with an arrow 4B in FIG. 5. InFIG. 4B, the magnets 72 of the VCM 70 are fixed onto thecarrier/follower 60 side. The coil of the VCM 70 comprises the coil body74A and its supporting part 74B. The supporting part 74B is fixed to aconnecting plate 92 (a plate vertical to the XY plane) which is rigidlylaid across the two rectangular blocks 90A and 90B. A center line KX ofthe VCM 70 shows the direction of the driving force of the coil 74, andwhen an electric current flows through the coil body 74A, the coil 74displaces into either positive or negative movement in the Y directionin accordance with the direction of the current, and generates a forcecorresponding to the amount of the current. Normally, in a commonly usedVCM, a ring-like damper or bellows are provided between the coil andmagnet so as to keep the gap between the coil and magnet, but accordingto the present embodiment, that gap is kept by a follow-up motion of thecarrier/follower 60, and therefore, such supporting elements as a damperor bellows are not necessary.

[0101] In the present embodiment, capacitance gap sensors 13A and 13Bare provided as a positioning sensor 13 (see FIG. 6) as shown in FIG.4B. In FIG. 4B, electrodes for capacitance sensors are placed so as todetect the change in the gap in the X direction between the side surfaceof the rectangular blocks 90A and 90B facing each other in the Xdirection and the side surface of a case 70′ of the VCM 70. Such apositioning sensor 13 can be placed anywhere as far as it can detect thegap change in the Y direction between the carrier/follower 60 and thestage 14 (or the body 42). Furthermore, the type of the sensor can beany of a non-contact type such as, for example, photoelectric,inductive, ultrasonic, or air-micro system.

[0102] The case 70′ in FIG. 4B is formed with the carrier/follower 60 inone, and placed (spatially) so as not to contact any member on thereticle stage 14 side. As for the gap between the case 70′ and therectangular blocks 90A and 90B in the X direction (scanning direction),when the gap on the sensor 13A side becomes wider, the gap on the sensor13B side becomes smaller. Therefore, if the difference between themeasured gap value by the sensor 13A and the measured gap value by thesensor 13B is obtained by either digital operation or analog operation,and a direct servo (feedback) control system which controls the drivingcurrent of the driving coil 68 for the carrier/follower 60 is designedusing a servo driving circuit which makes the gap difference zero, thenthe carrier/follower 60 will automatically perform a follow-up movementin the X direction always keeping a certain space to the stage body 42.Alternatively, it is also possible to design an indirect servo controlsystem which controls an electric current flow to the driving coil 68,with the operation of position control system 16 in FIG. 6 using themeasured gap value obtained only from one of the sensors and the Xcoordinate position of the stage 14 measured from the X axisinterferometer, without using the two gap sensors 13A and 13Bdifferentially.

[0103] In the VCM 70 as described in FIG. 4B, the gap between the coilbody 74A and the magnet 72 in the X direction (non-energizing direction)is in actuality about 2-3 mm. Therefore, a follow-up accuracy of thecarrier/follower 60 with respect to the stage body 42 would beacceptable at around ±0.5-1 mm. This accuracy depends on how much of theyaw rotation of the stage body is allowed, and also depends on thelength of the line in the KX direction (energizing direction) of thecoil body 74A of the VCM 70. Furthermore, the degree of the accuracy forthis can be substantially lower than the precise positioning accuracyfor the stage body 42 using an interferometer (e.g., ±0.03 μm supposingthe resolution of the interferometer is 0.01 μm). This means that theservo system for a follower can be designed fairly simply, and theamount of cost to install the follower control system would be small.Furthermore, the line KX in FIG. 4B is set so as to go through thecenter of gravity of the entire stage 14 on the XY plane, and each ofcenters of the pair of the air bearings 66A and 66B provided inside thesupport brackets 62 shown in FIG. 4 is also positioned on the line KX inthe XY plane.

[0104]FIG. 4C is a cross-sectional drawing of the part which includesthe guiding member 17, the carrier/follower 60, and the magnetic track56A sectioned from the direction of the arrow 4C in FIG. 2. The arm 24storing the magnetic track 56A is buoyed up and supported on the basesurface 12A by the air bearing 32, and the carrier/follower 60 is buoyedup and supported on the base surface 12A by the air bearing 66. At thistime, the height of the air bearing 48 at the bottom surface of thestage body 42 (see FIG. 3 or 5) and the height of the air bearing 32 aredetermined so as to place the driving coil 54A on the stage body 42 sidekeeping a 2-3 mm gap in the Z direction in the slot space of themagnetic track 56A.

[0105] Each of the spaces between the carrier/follower 60 and the arm 24in the Z and Y directions hardly changes because they are both guided bythe common guiding member 17 and the base surface 12A. Furthermore, evenif there is a difference in the height in the Z direction between thepart on the base surface 12A where the air bearing 32 at the bottomsurface of the driving frame 22 (arm 24) is guided and the part on thebase surface 12A where the air bearing 48 at the bottom surface of thestage body is guided, as long as the difference is precisely constantwithin the moving stroke, the gap in the Z direction between themagnetic track 56A and the driving coil 54A is also maintained constant.

[0106] Furthermore, since the driving coil 68 for the carrier/follower60 is originally fixed to the carrier/follower 60, it is arranged,maintaining a certain gap of 2-3 mm above and below in the slot space ofthe magnetic track 56A. The driving coil 68 hardly shifts in the Ydirection with respect to the magnetic track 56A.

[0107] Cables 82 (see FIG. 2) are provided for directing the signals tothe drive coils 54A and 54B on stage 14, the voice coil motor coil 74and the carrier/follower drive coil 68, and these cables 82 are mountedon the carrier/follower 60 and guide 17 thereby eliminating drag on thereticle stage 14. The voice coil motor 70 acts as a buffer by preventingtransmission of external mechanical disturbances to the stage 14.

[0108] Therefore, referring now to FIGS. 2 and 4A, the cable issues willbe described further in detail. As shown in FIG. 2, a connector 80 whichconnects wires of the electric system and tubes of the air pressure andthe vacuum system (hereafter called “cables”) is mounted on the basestructure 12 on one end of the guiding member 17. The connector 80connects a cable 81 from the external control system (including thecontrol system of the air pressure and the vacuum systems besides theelectric system control system shown in FIG. 6) to a flexible cable 82.The cable 82 is further connected to the end part 60E of thecarrier/follower 60, and electric system wires and the air pressure andthe vacuum system tubes necessary for the stage body 42 are distributedas the cable 83.

[0109] As mentioned before, the VCM 70 works to cancel a cable's drag oran influence by tension, but sometimes its influence appears as a momentin an unexpected direction between the carrier/follower 60 and the stagebody 42. In other words, the tension of the cable 82 gives thecarrier/follower 60 a force to rotate the guiding surface of the guidingmember 17 or the base surface 12A, and the tension of the cable 83 givesa force to the carrier/follower 60 and the stage body to rotaterelatively.

[0110] One of these moments, the constituent which shifts thecarrier/follower 60, is not problematic, but the one which shifts thestage body in X, Y, or θ direction (yaw rotation direction) could affectthe alignment or overlay accuracy. As for the X and θ directions, shiftscan be corrected by a consecutive drive by the two linear motors (54A,56A, 54B, 56B), and as for in the Y direction, the shift can becorrected by the VCM 70. In the present embodiment, since the weight ofthe entire stage 14 can be reduced substantially, the response of themotion of the stage 14 by VCM 70 in the Y direction and the response bythe linear motor in X and θ directions will be extremely high incooperation with the completely non-contact guideless structure.Furthermore, even when a micro vibration (micron order) is generated inthe carrier/follower 60 and it is transferred to the stage 14 via thecable 83, the vibration (from several Hz to tens of Hz) can besufficiently canceled by the above mentioned high response.

[0111] Now, FIG. 4A shows how each of the cables is distributed at thecarrier/follower 60. Each of the driving signals to the driving coils54A, 54B for the stage body 42 and the driving coil 74 of the VCM 70 andthe detection signal from the position sensor 13 (the gap sensors 13A,13B) go through the electric system wire 82A from the connector 80. Thepressure gas and the vacuum to each of the air bearings 48 and 66 gothrough the pneumatic system tube 82B from the connector 80. On theother hand, the driving signal to the driving coils 54A and 54B goesthrough the electric system wire 83A which is connected to the stagebody 42, and the pressurized gas for the air bearing 48 and the vacuumfor the clamping member 42C go through the pneumatic system hoses 83B.

[0112] Furthermore, it is preferable to have a separate line for thepneumatic system for the air bearings 20, 20′ and 32 of the drivingframe 22, independent of the one shown in FIG. 2. Also, as shown in FIG.4A, in case the tension or vibration of the cable 83 cannot beprevented, it is advisable to arrange the cable 83 so as to limit themoment by the tension or vibration the stage body 42 receives only tothe Y direction as much as possible. In that case, the moment can becanceled only by the VCM 70 with the highest response.

[0113] Referring now to FIGS. 1, 2 and 6, the positioning of the reticlestage 14 is accomplished first knowing its existing position utilizingthe laser interferometer system 15. Drive signals are sent to thereticle stage drive coils 54A and 54B for driving the stage 14 in the Xdirection. A difference in the resulting drive to the opposite sides 42Aand 42B of the reticle stage 14 will produce small yaw rotation of thereticle stage 14. An appropriate drive signal to the voice coil 72 ofvoice coil motor 70 produces small displacements of the reticle stage 14in the Y direction. As the position of the reticle stage 14 changes, adrive signal is sent to the carrier/follower coil 68 causing thecarrier/follower 60 to follow the reticle stage 14. Resulting reactionforces to the applied drive forces will move the magnetic track assemblyor drive frame 22 in a direction opposite to the movement of the reticlestage 14 to substantially maintain the center of gravity of theapparatus. It will be appreciated that the counter-weight or reactionmovement of the magnetic track assembly 22 need not be included in theapparatus in which case the magnetic track assembly 22 could be fixedlymounted on the base 12.

[0114] As described above, in order to control the stage systemaccording to the present embodiment, a control system as shown in FIG. 6is installed. This control system in FIG. 6 will be further explained indetail here. X1 driving coil and X2 driving coil composed as the drivingcoils 54A and 54B of two linear motors respectively, and Y driving coilcomposed as the driving coil 72 of the VCM 70 are placed in the reticlestage 14, and the driving coil 68 is placed in the carrier/follower 60.Each of these driving coils is driven in response to the driving signalsSX1, SX2, SY1 and SΔX, respectively, from the position control system16. The laser interferometer system 15 which measures the coordinatesposition of the stage 14 comprises the Y axis interferometer whichsends/receives the beam LBY, the X1 axis interferometer whichsends/receives the beam LBX1, and the X2 axis interferometer whichsends/receives the beam LBX2, and they send position information foreach of the directions of the axes, IFY, IFX1, IFX2 to the positioncontrol system 16. The position control system 16 sends two drivingsignals SX1 and SX2 to the driving coils 54A and 54B so that thedifference between the position information IFX1 and IFX2 in the Xdirection will become a preset value, or in other words, the yawrotation of the reticle stage 14 is maintained at the specified amount.Thus, the yaw rotation (in θ direction) positioning by the beams LBX1and LBX2, X1 axis and X2 axis interferometers, the position controlsystem 16, and the driving signals SX1 and SX2 is constantly beingconducted, once the reticle 44 is aligned on the stage body 42, needlessto mention the time of the exposure.

[0115] Furthermore, the control system 16, which obtained the currentcoordinate position of the stage 14 in the X direction from the averageof the sum of position information IFX1 and IFX2 in the X direction,sends the driving signals SX1, SX2 to the driving coils 54A and 54B,respectively, based on the various commands from the Host CPU 16′ andthe information CD for the parameters. Especially when scanning exposureis in motion, it is necessary to move the stage 14 straight in the Xdirection while correcting the yaw rotation, and the control system 16controls the two driving coils 54A and 54B to give the same or slightlydifferent forces as needed.

[0116] Furthermore, the position information IFY from the Y axisinterferometer is also sent to the control system 16, and the controlsystem 16 sends an optimum driving signal SΔX to the driving coil 68 ofthe carrier/follower 60. At that time, the control system 16 receivesthe detection signal S_(pd) from the position sensor 13 which measuresthe space between the reticle stage 14 and the carrier/follower 60 inthe X direction, and sends a necessary signal SAX to make the signalS_(pd) into the preset value as mentioned before. The follow-up accuracyfor the carrier/follower 60 is not so strict that the detection signalS_(pd) of the control system 16 does not have to be evaluated strictlyeither. For example, when controlling the motion by reading the positioninformation IFY, IFX1, IFX2 every 1 millisecond from each of theinterferometers, the high speed processor in the control system 16samples the current of the detection signal S_(pd) each time, determineswhether the value is large or small compared to the reference value(acknowledge the direction), and if the deviation surpasses a certainpoint, the signal SΔX in proportion to the deviation can be sent to thedriving coil 68. Furthermore as mentioned before, it is also acceptableto install a control system 95 which directly servo controls the drivingcoil 68, and directly controls the follow-up motion of thecarrier/follower 60 without going through the position control system16.

[0117] Since the moving stage system as shown has no attachment toconstrain it in the X direction, small influences may cause the systemto drift toward the positive or negative X direction. This would causecertain parts to collide after this imbalance became excessive. Theinfluences include cable forces, imprecise leveling of the basereference surface 12A or friction between components. One simple methodis to use weak bumpers (not shown) to prevent excessive travel of thedrive assembly 22. Another simple method is to turn off the air to oneor more of the air bearings (32, 20) used to guide the drive assembly 22when the drive assembly reaches close to the end of the stroke. The airbearing(s) can be turned on when the drive begins to move back in theopposite direction.

[0118] More precise methods require monitoring the position of the driveassembly by a measuring device (not shown) and applying a driving forceto restore and maintain the correct position. The accuracy of themeasuring device need not be precise, but on the order of 0.1 to 1.0 mm.The driving force can be obtained by using another linear motor (notshown) attached to the drive assembly 22, or another motor that iscoupled to the drive assembly.

[0119] Finally, the one or more air bearings (66, 66A, 66B) of thecarrier/follower 60 can be turned off to act as a brake during idleperiods of the stage 42. If the coil 68 of the carrier/follower 60 isenergized with the carrier/follower 60 in the braked condition, thedrive assembly will be driven and accelerated. Thus, the positioncontrol system 16 monitors the location of the drive assembly 22. Whenthe drive assembly drifts out of position, the drive assembly isrepositioned with sufficient accuracy by intermittently using the coil68 of the carrier/follower 60.

[0120] In the first embodiment of the present invention, the drivingframe 22 which functions as a counter weight is installed in order toprevent the center of gravity of the entire system from shifting, andwas made to move in the opposite direction from the stage body 42.However, when the structures in FIGS. 1-5 are applied to a system wherethe shift of the center of gravity is not a major problem, it is alsoacceptable to fix the driving frame 22 on the base structure 12together. In that case, except for the problem regarding the center ofgravity, some of the effects and function can be applied without makingany changes.

[0121] This invention provides a stage which can be used for highaccuracy position and motion control in three degrees of freedom in oneplane: (1) long linear motion; (2) short linear motion perpendicular tothe long linear motion; and (3) small yaw rotation. The stage isisolated from mechanical disturbances of surrounding structures byutilizing electromagnetic forces as the stage driver. By further using astructure for this guideless stage, a high control bandwidth isattained. These two factors contribute to achieve the smooth andaccurate operation of the stage.

[0122] Bearing in mind the description of the embodiment illustrated inFIGS. 1-6, one preferred embodiment of the present invention isillustrated in FIGS. 7 and 8, wherein the last two digits of thenumbered elements are similar to the corresponding two digit numberedelements in FIGS. 1-5.

[0123] In FIGS. 7 and 8, differing from the previous first embodiment,the driving frame which functions as a counter weight is removed, andeach of the magnet tracks 156A and 156B of the two linear motors isrigidly mounted onto the base structure 112. The stage body 147 whichmoves straight in the X direction is placed between the two magnetictracks 156A and 156B. As shown in FIG. 8, an opening 112B is formed inthe base structure 112, and the stage body 142 is arranged so as tostraddle the opening 112B in the Y direction. There are four pre-loadedair bearings 148 fixed on the bottom surface at both ends of the stagebody 142 in the Y direction, and they buoy up and support the stage body142 against the base surface 112A.

[0124] Furthermore, according to the present embodiment, the reticle 144is clamped and supported on a reticle chuck plate 143 which isseparately placed on the stage body 142. The straight mirror 150Y forthe Y axis laser interferometer and two corner mirrors 150X1, 150X2 forthe X axis laser interferometer are mounted on the reticle chuck plate143. The driving coils 154A and 154B are horizontally fixed at both endsof the stage body 142 in the Y direction with respect to the magnetictracks 156A and 156B, and due to the control subsystem previouslydescribed, make the stage body 142 run straight in the X direction andyaw only to an extremely small amount.

[0125] As evident from FIG. 8, the magnetic track 156B of the right sideof the linear motor and the magnetic track 156A of the left side of thelinear motor are arranged so as to have a difference in level in the Zdirection between them. In other words, the bottom surface of both endsin the direction of the long axis of the magnetic track 156 on the leftside is, as shown in FIG. 7, elevated by a certain amount with a blockmember 155 against the base surface 112A. The carrier/follower 160 wherethe VCM 170 is fixed is arranged in the space below the elevatedmagnetic track 156A.

[0126] The carrier/follower 160 is buoyed up and supported by thepre-loaded air bearings 166 (at 2 points) on the base surface 112A′ ofthe base structure 112 which is one level lower. Furthermore, twopre-loaded air bearings 164 against the vertical guiding surface 117A ofthe straight guiding member 117, which is mounted onto the basestructure 112, are fixed on the side surface of the carrier/follower160. This carrier/follower 160 is different from the one in FIG. 4Aaccording to the previous embodiment, and the driving coil 168 (FIG. 7)for the carrier/follower 160 is fixed horizontally to the part whichextends vertically from the bottom of the carrier/follower 160, andpositioned in the magnetic flux slot of the magnetic track 156A withoutany contact. The carrier/follower 160 is arranged so as not to contactany part of the magnetic track 156A within the range of the movingstroke, and has the VCM 170 which positions the stage body 142 preciselyin the Y direction.

[0127] Furthermore, in FIG. 7, the air bearing 166 which buoys up andsupports the carrier/follower 160 is provided under the VCM 170. Thefollow-up motion to the stage body 142 of the carrier/follower 160 isalso done based on the detection signal from the position sensor 13 asin the previous embodiment.

[0128] In the second embodiment structured as above, there is aninconvenience where the center of gravity of the entire system shifts inaccordance with the shift of the stage body 142 in the X direction,since there is substantially no member which functions as a counterweight. It is, however, possible to position the stage body 142precisely in the Y direction with non-contact electromagnetic force bythe VCM 170 by way of following the stage body 142 without any contactusing the carrier/follower 160. Furthermore, since the two linear motorsare arranged with a difference in the level in the Z direction betweenthem, there is a merit where the sum of the vectors of the force momentgenerated by each of the linear motors can be minimized at the center ofgravity of the entire reticle stage because the force moment of each ofthe linear motors substantially cancels with the other.

[0129] Furthermore, since an elongated axis of action (the line KX inFIG. 4B) of the VCM 170 is arranged so as to pass through the center ofgravity of the entire structure of the stage not only on the XY planebut also in the Z direction, it is more difficult for the driving forceof the VCM 170 to give unnecessary moment to the stage body 142.Furthermore, since the method of connecting the cables 82, 83 via thecarrier/follower 160 can be applied in the same manner as in the firstembodiment, the problem regarding the cables in the completelynon-contact guideless stage is also improved.

[0130] The same guideless principle can be employed in anotherembodiment. For example, in schematic FIGS. 9 and 10, the stage 242,supported on a bases 212, is driven in the long X direction by a singlemoving coil 254 moving within a single magnetic track 256. The magnetictrack is rigidly attached to the base 212. The center of the coil islocated close to the center of gravity of the stage 242. To move thestage in the Y direction, a pair of VCMs (274A, 274B, 272A, 272B) areenergized to provide an acceleration force in the Y direction. Tocontrol yaw, the coils 274A and 274B are energized differentially undercontrol of the electronics subsystem. The VCM magnets (272A, 272B) areattached to a carrier/follower stage 260. The carrier/follower stage 260is guided and driven like the first embodiment previously described.This alternative embodiment can be utilized for a wafer stage. Where itis utilized for a reticle stage the reticle can be positioned to oneside of the coil 254 and track 256, and if desired to maintain thecenter of gravity of the stage 242 passing through the coil 254 andtrack 256, a compensating opening in the stage 242 can be provided onthe opposite side of the coil 254 and track 256 from the reticle.

[0131] Merits gained from each of the embodiments can be roughly listedas follows. To preserve accuracy, the carrier/follower design eliminatesthe problem of cable drag for the stage since the cables connected tothe stage follow the stage via the carrier/follower. Cables connectingthe carrier/follower to external devices will have a certain amount ofdrag, but the stage is free from such disturbances since there is nodirect connection to the carrier/follower which acts as a buffer bydenying the transmission of mechanical disturbances to the stage.

[0132] Furthermore, the counter-weight design preserves the location ofthe center of gravity of the stage system during any stage motion in thelong stroke direction by using the conservation of momentum principle.This apparatus essentially eliminates any reaction forces between thestage system and the base structure on which the stage system ismounted, thereby facilitating high acceleration while minimizingvibrational effects on the system.

[0133] In addition, because the stage is designed for limited motion inthe three degrees of freedom as described, the stage is substantiallysimpler than those which are designed for full range motions in allthree degrees of freedom. Moreover, unlike a commutatorless apparatus,the instant invention uses electromagnetic components that arecommercially available. Because this invention does not requirecustom-made electromagnetic components which become increasinglydifficult to manufacture as the size and stroke of the stage increases,this invention is easily adaptable to changes in the size or stroke ofthe stage.

[0134] The embodiment with the single linear motor eliminates the secondlinear motor and achieves yaw correction using two VCMs.

[0135] The following explains another embodiment of this invention withreference to FIGS. 11-29B. In this example, the invention is applied toa step-and-scan type projection exposure apparatus.

[0136]FIG. 11 shows a projection apparatus of this example. In thisfigure, during exposure, exposure light such as i rays of a mercurylamp, excimer laser light or the like such as KrF, ArF, F₂, or the likefrom an illumination optical system (not depicted) illuminates anillumination area of a pattern face of a reticle 301. Furthermore, apattern image within the illumination area of the reticle 301 isprojected and exposed on the top of the wafer 303 on which photoresistis coated, at a predetermined projection magnification β (β is normally¼, ⅕, or the like) through a projection optical system 302. Hereafter,an explanation is given with the Z-axis defined as being parallel to anoptical axis AX of the projection optical system 302 in a non-vibratingstate, and with the X-axis and Y-axis defining a perpendicularcoordinate system within a plane perpendicular to the optical axis AX.

[0137] First, the reticle 301 is held on the reticle stage 304, and whenthe reticle stage 304 continuously moves in the X direction (scanningdirection) by a linear motor method on the reticle base 309, amicro-adjustment of the position of the reticle 301 is performed withinthe XY plane. The two-dimensional position of the reticle stage 304(reticle 301) is measured by moving mirrors 343X and 343Y and laserinterferometers 318X and 318Y on the reticle stage 304. This measuredvalue is supplied to a main controller 350 comprising a computer thatcontrols an operation of the device as a whole. The main controller 350controls the position and the moving speed of the reticle stage 4through the reticle stage controller 352, based upon the measured value.

[0138] Meanwhile, a wafer 303 is held on top of a wafer stage 305 byvacuum absorption, and the wafer stage 305 is disposed on a wafer base307 via three support legs 331A-331C, which can freely extend andretract within a specified range in the Z direction. The extending orretracting amount of the support legs 331A-331C is controlled by asupport leg controller 363 (see FIG. 26). By making the extending orretracting amount of the support legs 331A-331C the same, the positionof the Z direction of the wafer 303 (focus position) is controlled.Controlling of the tilt angle (leveling) of the surface of the wafer 303can be performed by controlling the extending or retracting amount ofthe support legs 331A-331C independently.

[0139] The wafer stage 305 can continuously move on the wafer base 307in the X and Y directions by, for example, a linear motor method.Additionally, stepping can also be performed by the continuous movement.Furthermore, in order to perform coordinate measurement of the wafer 303(wafer stage 305), an X-axis moving mirror 344X (see FIG. 13) with areflecting surface that is substantially perpendicular to the X-axis anda Y-axis moving mirror 344Y (see FIG. 13) with a reflecting surface thatis substantially perpendicular to the Y-axis are fixed to a side surfaceof the wafer stage 305. Corresponding to these moving mirrors, an X-axisreference mirror 314 and a Y-axis reference mirror 313 are fixed to aside surface of the projection optical system 302.

[0140] During scanning exposure, the reticle stage 304 is moved atconstant velocity in the X-axis direction and, in synchronization withthis movement, the wafer stage 305 on which the wafer 303 is disposed ismoved in the opposite direction at a speed that is reduced by theprojection magnification β of the moving speed of the reticle stage 304,and scanning exposure is performed. After completion of the scanningexposure, the wafer stage 305 step-moves in the scanning direction or inthe Y-axis direction that is perpendicular to the scanning direction.The reticle stage 304 and the wafer stage 305 are moved insychronization in a direction opposite to the previous direction, andscanning exposure is performed. Hereafter, a pattern image of thereticle 301 is transferred to all the shooting areas on the wafer 303 bythe same operation.

[0141] Next, the reticle stage and the reticle base of the exposureapparatus of this example are explained. The reticle stage 304 is aguideless stage which is disclosed in Japanese Laid-Open PatentPublication No. 8-63231 (corresponding to parent application Ser. No.08/698,827) and can be driven in rotational directions about the opticalaxis AX of the projection optical system 302 and about the X- and theY-axes. Furthermore, a pair of linear motors that drive the reticlestage 304 using a coil, which are fixed to a side surface of the reticlestage 304, and a pair of motor magnets 311A and 311B, which are fixed tothe top of the reticle base 309 are provided, and the reticle base 309is supported through a fluid bearing (not depicted) such as an airbearing with respect to a top surface 310 of a structural body 306. Endsof coil units 312A and 312B disposed on the top of the structural body306 are inserted from ends of the motor magnets 311A and 311B, and bythe pair of linear motors structured by the motor magnets 311A and 311Band the coil units 312A and 312B, the reticle base 309 is positioned inthe X-axis direction with respect to the structural body 306.Furthermore, the structural body 306 is supported on the floor byvibration control pads 349 through four legs 306 a, decreasing thevibration from the floor.

[0142] When the reticle stage 304 moves during the scanning exposure,when the driving reaction added by the motor magnets 311A and 311B isreceived, the reticle base 309 moves, so as to maintain a momentum inthe direction opposite to the moving direction of the reticle stage 304,by the linear motor that has the coil units 312A and 312B. For example,if the masses of the reticle stage 304 and the reticle base 309 are 20kg and 1000 kg, respectively, and the reticle base 309 thus has a mass50 times that of the reticle stage 304, if the reticle stage 304 movesby approximately 300 mm during scanning, the reticle base 309 moves inthe direction opposite to the moving direction of the reticle stage 304by approximately 6 mm. By moving the reticle stage 304 and the reticlebase 309, so as to maintain the momentum, transmission of the drivingreaction to the structural body 306 of the reticle stage 304 can beprevented, and occurrence of vibration, which is a cause of disturbanceduring the positioning of the reticle stage 304, can be prevented.Furthermore, the displacement amount of the reticle base 309 isconstantly measured by a linear encoder (not depicted), and a currentsignal is formed when the reticle stage 304 is driven, based upon thismeasured value.

[0143] Furthermore, in the projection exposure apparatus of thisexample, there is no movement of the center of the gravity of the systemabove the reticle base 309, so there is no fluctuation of the load tothe structural body 306 that supports the reticle base 309, and theposition of the reference mirrors 313 and 314 used for the measurementof the relative position between the reticle stage 304 and theprojection optical system 302 does not fluctuate. Furthermore, when thereticle base 309 is displaced a specified amount or more, if itmechanically interferes with other members, it is acceptable toconstantly maintain the reticle base 309 at a substantially constantposition while controlling the coil units 312A and 312B, which areelectromagnetic driving parts disposed between the reticle base 309 andthe structural body 306, and decreasing the vibration transmitted to thestructural body 306. By doing this, it is possible to prevent thereticle base 309 from interfering with other members.

[0144] Next, a method of supporting the projection optical system of theexposure apparatus of this example is explained. FIG. 12 shows theprojection optical system 302 of the exposure apparatus of this example.In this figure, the point at which the object plane 315 and the imagesurface 316 are internally divided at the reduction projectionmagnification ratio β (=a/b) on the optical axis AX is defined as areference point 317 of the projection optical system 302. This referencepoint 317 is defined as a center, and even if the projection opticalsystem 302 is minutely rotated about an arbitrary axis within a planethat is orthogonal to the optical axis AX, the position relationshipbetween the object plane 315 and the image surface 316 does not change.The centers of the reference mirrors 313 and 314 are set on a planeperpendicular to the optical axis AX which pass through this referencepoint 317, and a laser beam is irradiated to these centers. Accordingly,when the projection optical system 302 is slid by a disturbancevibration, the reference point 317 also moves.

[0145] Furthermore, the relative displacement between the reticle stage304 and the wafer stage 305 and the crossing point (reference mirrors313 and 314) of the plane perpendicular to the optical axis AX of theprojection optical system 302 and the external surface of the lensbarrel surrounding the projection optical system 302 are constantlymeasured by the laser interferometers 318X and 318Y. By controlling thereticle stage 304 and the wafer stage 305 so as to match the measuredvalue with a desired value, it is possible to prevent position shiftingof a pattern to be formed on the wafer 302.

[0146] Furthermore, the bottom part of the projection optical system 302passes through an opening of a support plate 306 b which is disposedbetween the legs 306 a, and is spaced from the opening by a gap.Additionally, the support part of the projection optical system 302 isformed by three flexible rods 319A-319C extending from the structuralbody 306. The extended lines of the respective rods 319A-319C cross atone point, which coincides with the reference point 317. Accordingly,even if the projection optical system 302 is slid by receiving adisturbance vibration, the projection optical system 302 is minutelyrotated using the center of the reference point 317 as a center ofrotation, so the position in the X and Y directions of the referencemirrors 313 and 314 hardly changes. Furthermore, because the rods319A-319C are flexibly structured, high frequency vibrations dissipate,and hardly any deterioration of the contrast occurs during transfer ofthe pattern.

[0147] Next, the wafer stage of the exposure apparatus of this exampleis explained.

[0148] As shown in FIG. 11, the wafer stage 305 is positioned on top ofthe wafer base 307, and the wafer base 307 is supported by an elevatordriving part 308 that can displace several hundred μm in the verticaldirection. Between the wafer base 307 and the elevator driving part 308,a visco-elastic body (not depicted) is provided, and vibration from thefloor can be decreased. In addition, on the wafer base 307, five speedsensors (two of the five speed sensors, 336A and 336B, are shown in FIG.26) are provided, and the movement of the wafer stage 305 can bemeasured. It is also acceptable to use acceleration sensors instead ofspeed sensors.

[0149] FIGS. 13A-13D show the wafer stage 305 of the exposure apparatusof this example by enlargement. FIG. 13A is a plan view of the wafertable 320. FIG. 13B is a cross-sectional view of FIG. 13A along lineB-B. FIG. 13C is a front view (however, a carrier 321 is not depicted)of FIG. 13A. FIG. 13D is a cross-sectional view of FIG. 13A along lineD-D. First, in FIG. 13D, the wafer stage 305 has a wafer table 320 onwhich a wafer 303 is disposed and a carrier 321 that carries adriving/guiding part of the wafer table 320. The carrier 321 is movableon the wafer base 307 and can be driven in the X and Y directions by apulse motor type of planar motor (for example, a Sawyer motor). In thisexample, when the carrier 321 is driven, a pulse motor (not depicted) isused to supply pulses according to the distance to a desired position bythe open loop method. Because the pulses to a desired position is outputto a motor controller, it is not necessary to provide a new positionmeasurement device for the carrier 321. Furthermore, it is alsoacceptable to use an ultrasonic wave motor as a flat motor.

[0150] Meanwhile, as shown in FIG. 13A, on the top surface of the wafertable 320, a plurality of parallel shallow grooves 339 are disposed tovacuum absorb the wafer 303. Many holes in the shallow grooves 339 arein communication with a vacuum pump, which is not depicted. Furthermore,deep grooves 338 to receive the wafer carrier arms, described later, aredisposed in spaces between four shallow grooves 339 without interferingwith the shallow grooves 339. When a wafer 303 is fixed on the wafertable 320, the wafer carrier arm used as the carrier of the wafer 303can be taken in and out without interfering with the wafer table 320.

[0151] Furthermore, as shown in FIG. 13B, a guide shaft 322B is disposedin the scanning direction (X direction) via a support member 322C on thecarrier 321. A guide member 322A is fixed to the bottom surface of thewafer table 320, with the guide shaft 322B passing therethrough. Thewafer table 320 is restricted by a non-contact guide (for example, afluid bearing or a magnetic bearing) comprising the guide member 322A,which guides the wafer table 320 on the carrier 321 in the X direction,and the guide shaft 322B. Furthermore, in FIG. 13D, a pair of linearmotors 323A, 324A, and 323B, 324B are structured by coils 323A and 323Bfixed to the carrier 321 and magnets 324A and 324B fixed to the bottomsurface of the wafer table 320. The wafer table 320 is driven in the Ydirection and the rotational direction by the linear motors 323A, 324A,and 323B, 324B, which serve as non-contact electromagnetic drivingparts. The displacement of the wafer table 320 with respect to thecarrier 321 is measured by a linear encoder (not depicted), which servesas a non-contact position measurement device. Furthermore, the guideshaft 322B is structured so as to be rotatable about the guide axis by arotation member 322D. Additionally, when the linear motors 323A, 324Aand 323B, 324B generate a driving force in the same direction, the wafertable 320 moves in the guide axis direction (X direction). Conversely,when the linear motors 323A, 324A, and 323B, 324B generate a drivingforce in different directions, respectively, the wafer table 320 isrotated about the center of gravity.

[0152] The center of the thrust of the linear motors 323A, 324A, and323B, 324B and the center of the guide member 322A are disposed so thatthey can be positioned in a plane parallel to the top surface of thewafer base 307, and includes the center of gravity of the wafer table320. Therefore, unnecessary inclination of the wafer table does notoccur at the time of acceleration of the wafer table 320. Furthermore,the size of the guide shaft 22B and the linear motors 323A, 324A, and323B, 324B, only needs to be long enough for the movement of the waferduring the scanning exposure. Therefore, the size can be small so as tostore the carrier 321 below the wafer table 320, and the wafer can bemoved at high speed with high accuracy.

[0153] Furthermore, because the positioning accuracy needed forreceiving the wafer 303 is approximately several μm, measurement by alaser interferometer is not particularly needed in the area thatreceives the wafer 303, and the resolution of the pulse motor and/or theresolution of the position measurement device of the carrier 321 issufficient. Therefore, the moving mirrors 344X and 344Y which areprovided for the wafer table 320 of FIG. 13 for the laserinterferometers 318X and 318Y do not necessarily have to cover theentire moving area of the wafer table 320. Only the length of the areain which precise positioning in nm units is needed, that is, the lengthof the diameter of the wafer 303, is needed.

[0154] The moving mirrors 344X and 344Y for the laser interferometer 318are disposed on side surfaces of the wafer table 320 of this example,and the rotational angle about the Z-axis and the position of the wafertable 320 are measured. Side surfaces of the wafer table 320 are used asmoving mirrors 344X and 344Y for the laser interferometers 318X and318Y, so the wafer table 320 is of a size that substantiallycircumscribes the wafer 303, and it is extremely small and light,compared to a conventional wafer table. Furthermore, when the wafertable 320 is structured so as to dispose a rib structure in the bottomsurface with a thickness of approximately 3 mm by using a siliconcarbide, the weight of the wafer table 320 is approximately 5 kg.

[0155]FIG. 14 is a block diagram showing a structure of a controllerthat controls both the wafer table 320 and the carrier 321. In FIG. 14,the main controller 350 supplies desired positions of the carrier 321and the wafer table 320, respectively, to subtractors 354 and 357 withinthe wafer stage controller 325. Furthermore, the relative displacementamount of the wafer table 320 with respect to the carrier 321 isdetected by a hypothetical subtractor 356 and a displacement sensor(linear encoder) 360. A table controller 355 drives the wafer table 320,based upon the output of the subtractor 354 and the displacement sensor360, and the carrier controller 358 drives the carrier 321 based uponthe output of the subtractor 357. The subtractor 354 outputs a valuecorresponding to the measured value of the laser interferometers 318Xand 318Y subtracted from the desired value, and the subtractor 357outputs a value that corresponds to the measured value of a hypotheticallinear encoder 359 for the carrier 321 subtracted from the desiredvalue.

[0156] When the laser interferometers 318X and 318Y (see FIG. 11) arenot used while the mode switch 326 is OFF, that is, in the case of theapproximate positioning, based upon the signal from the displacementsensor 360 that serves as a linear encoder, the wafer stage controller325 controls the linear motors 323A, 324A and 323B, 324B of FIGS.13A-13D so as to constantly position the wafer table 320 at the middlepoint of the moving range with respect to the carrier 321. Furthermore,when the driving part of the carrier 321 has an encoder 359, the carriercontroller 358 moves the carrier 321 to a desired position withreference to the encoder 359. When an encoder is not especiallyprovided, such as in the case of a pulse motor in this example, pulsesto a desired position are output to the motor controller and the carrier321 is controlled. Therefore, regardless of the existence of an encoder,the wafer table 320 is controlled so as to be moved while following themovement of carrier 321.

[0157] When the mode switch 326 of FIG. 14 is in the ON state and thewafer table 320 moves based upon the measured value of the laserinterferometers 318X and 318Y, that is, in the case of precisepositioning, based upon the output of the subtractor 354, whichreferences the measured value of the laser interferometers 318X and318Y, the table controller 355 causes the linear motors 323A, 324A and323B, 324B to generate thrust with respect to the wafer table 320, andcauses the wafer table 320 to move. Furthermore, the carrier 321 iscontrolled just like in the approximate positioning.

[0158] When the wafer table 320 moves at constant velocity while usingthe laser interferometers 318X and 318Y, that is, at the time ofscanning exposure, the table controller 355 causes the linear motors323A, 324A and 323B, 324B to generate thrust and move the wafer table320 while referring to the output of the subtractor 354, which hassubtracted the measured value of the laser interferometers 318X and318Y. At this time, the carrier 321 maintains a still state, and onlythe wafer table 320 moves at a constant velocity. Therefore, it is onlythe light weight wafer table 320 that generates the driving reactionwith respect to the wafer base 307 during the scanning exposure, so thedisturbance reaction to be generated becomes extremely small, andscanning exposure can be performed at high speed with high accuracy.

[0159] Next, the guide member 322A and the guide shaft 322B of the wafertable 320 of the exposure apparatus of this example are explained.

[0160]FIG. 15A-C show the guide member 322A and the guide shaft 322B ofFIGS. 13A-D by enlargement. In this figure, springs 327A and 327B areprovided as elastic bodies at both ends of the guide shaft 322B. Whenthe wafer table 320 reciprocates with respect to the carrier 321, first,as shown in FIG. 15A, kinetic energy of the wafer table 320 is convertedto potential energy via the guide member 322A and is stored in thespring 327A. Next, as shown in FIG. 15B, the potential energy that hasbeen stored in the spring 327A is again converted to kinetic energy ofthe wafer table 320, and the wafer stage controller 325 of FIG. 11controls the wafer table 320 using the kinetic energy so that it movesthe wafer table 320 at the speed of −V. Furthermore, as shown in FIG.15C, when the support member 322A contacts the spring 327B, an opposingforce of +F occurs in the spring 327B and the kinetic energy of thewafer table 320 is again converted to potential energy and is saved inthe spring 327B. Therefore, mechanical energy to be consumed in the caseof reciprocation of the wafer table 320 is mainly only the heat from theviscosity resistance of the wafer table 320 with respect to the air, andfrom when the elastic bodies are deformed. Thus, the heating amount ofthe linear motors 323A, 324A, and 323B, 324B becomes extremely small.

[0161]FIG. 16A shows a speed curve of the wafer table 320 when themoving speed of the wafer table 320 is shifted to a constant speed (0.5m/s) and is moved on the guide shaft 322B, which is hypotheticallydefined as a guide axis without an elastic body. In FIG. 16A, thehorizontal axis shows time t (s), and the vertical axis shows the movingspeed V (m/s) of the wafer table 320. Furthermore, FIG. 16B shows thethrust of the linear motors 323A, 324A and 323B, 324B at that time. InFIG. 16B, the horizontal axis is time t (s), and the vertical axis is athrust F(N) of the linear motors. Furthermore, the mass of the wafertable 320 which is used is 5 kg. FIG. 17A corresponds to FIG. 16A andshows a speed curve of the wafer table 320 calculated assuming the casewhere an ideal wafer table 320 without vibration is accelerated to acertain speed on the guide axis provided with a specified spring. FIG.17B shows a thrust F(N) of the linear motors 323A, 324A and 323B, 324B,which is calculated assuming the case where a wafer table 320 thatresonates is controlled with the speed curve of FIG. 17A as the speedgoverning value. When FIGS. 16A-B are compared with FIGS. 17A-B, theratio of the heating amount of the linear motors 323A, 324A, and 323B,324B is 1:0.94, which is substantially the same.

[0162]FIG. 18A shows a speed curve when the speed curve of FIG. 17A isthe speed governing value, the guide shaft 322B provided with thesprings 327A and 327B of FIG. 15 is used, and the wafer table 320 isaccelerated to a constant speed. FIG. 18B shows the thrust of the wafertable 320 and thrust generated by the linear motors 323A, 324A and 323B,324B. In FIG. 18B, the horizontal axis is time t (s), and the verticalaxis is thrust F(N). The curve A in a solid line is the thrust added tothe wafer table 320, and the curve B in the single-dot chain line showsthe thrust of the linear motors 323A and 323B. The spring constant ofthe springs 327A and 327B is 1,000 N/m, and this is 40% of an idealspring constant (2,500 N/m). By using the springs 327A and 327B, theheating amount of the linear motors 323A, 324A and 323B, 324B can bereduced to approximately 35% of the heating amount of the case when anelastic body is not used.

[0163]FIG. 19A shows a speed curve when the wafer table 320 isaccelerated to a constant speed using a guide shaft 322B with springs327A and 327B with the optimum spring constant value of 2,500 N/m. FIG.19B shows the thrust F of the wafer table 320 at that time. The heatingamount of the linear motors 323A, 324A and 323B, 324B can be reduced to1% or less of the case when an elastic body is not used. Thus, by havingthe springs 327A and 327B at both ends of the guide shaft 322B, theheating amount of the linear motors 323A, 324A and 323B, 324B can bereduced when the wafer table 320 constantly moves.

[0164] However, in the case of the still-positioning of the wafer table320 at the end of the guide shaft 322B, the linear motors 323A, 324A and323B, 324B need to generate a thrust that can be balanced with theresistance of the springs 327A and 327B, which causes the heating amountof the linear motors 323A, 324A and 323B, 324B to increase.

[0165]FIG. 20 shows the resistance of the springs 327A and 327B at theend of the guide shaft 322B provided with the springs 327A and 327B. InFIG. 20, the horizontal axis shows distance D(m) from the end of theguide shaft 322B, and the vertical axis shows the resistance F_(P)(N) ofthe springs 327A and 327B. In order to still-position the wafer table320 at the end of the guide shaft 322B, the linear motors 323A, 324A and323B, 324B need to generate a thrust (50 N) that is large enough tobalance the resistance of the springs 327A and 327B. Otherwise, theheating amount increases. Therefore, in this case, a magnetic member isfixed to the end of the guide shaft 322B. Preferably, the heating amountis reduced when the wafer table 320 is still-positioned by using theattractive force of the magnet member.

[0166] FIGS. 21A-C show the guide member 322A and the guide shaft 322Bto which the magnetic member is fixed, corresponding to FIGS. 15A-C. InFIGS. 21A-C, steel plates 329 are fixed to both ends of the guide member322A, and magnets 330 are fixed at both ends of the guide shaft 322B. Asshown in FIGS. 21A-C, when the wafer table 320 is still-positioned atthe end of the guide shaft 322B via the guide member 322A, by using theattraction of the steel plate 329 and the magnet 330, the thrust of thelinear motors 323A, 324A and 323B, 324B needed against the resistance ofthe springs 327A and 327B can be reduced and the heating amount can becontrolled. Furthermore, in the case of moving the wafer table 320 at aconstant velocity, as shown in FIG. 21B, by using the resistance of thesprings 327A and 327B, the heating amount of the linear motors 323A,324A, and 323B, 324B is reduced. In this case, the heating amount of thelinear motors can be reduced to approximately ⅙ of the case when aspring or the like is not used on the guide shaft 322B. Additionally,when there is no limitation to the thrust of the linear motors, thepotential energy at both ends of the guide shaft 322B can be set at 0.Furthermore, the setting relationship between the steel plates 329 andthe magnets 330 can be reversed, and it is acceptable to disposeanything that generates attractive force opposing the resistance of theelastic member of the springs 327A and 327B or the like at the ends ofthe guide shaft 322B.

[0167]FIG. 22A shows a speed curve that is calculated assuming the casewhere an ideal wafer table 320 without vibration is accelerated to aconstant speed on a guide shaft 322B provided with springs, steelplates, and magnets. In FIG. 22A, the horizontal axis is time t(s), andthe vertical axis is moving speed V(m/s) of the wafer table 320. FIG.22B shows a thrust of the linear motors 323A, 324A and 323B, 324Bcalculated assuming the case where the wafer table 320 that resonates iscontrolled with the speed curve of FIG. 22A as the speed governingvalue. In FIG. 22B, the horizontal axis is time t(s), and the verticalaxis is thrust F(N) of the linear motors. FIG. 23A shows a speed curvewhen the speed curve of FIG. 22A is the speed governing value and thewafer table 320 is accelerated to a constant speed on the guide axis 322provided with the steel plates 329 and the magnets 330. FIG. 23B showsthe thrust F (curve A in solid line) that is added to the wafer table320 at that time, and the thrust F (curve B in single-dot chain line) ofthe linear motors 323A, 324A and 323B, 324B. The spring constant of thesprings 327A and 327B is 2,000 N/m, which is the optimum springconstant. The heating amount of the linear motors 323A, 324A and 323B,324B in this case is 1% or less of the case when springs, magnets, andsteel plates are not used. Furthermore, compared to the case where amagnet or the like is not provided, the thrust required at the start ofmoving is small and the wafer table 320 is gradually accelerated, sothere is an advantage such that the mechanical resonance of the wafertable 320 can be eased.

[0168]FIG. 24 shows the resultant force F_(P)(N) between the resistanceof the springs 327A and 327B and the attraction between the magnet 330and the steel plate 329 at an end of the guide shaft 322B to which thesteel plate 329 and the magnet 330 are fixed according to FIG. 20. InFIG. 24, the horizontal axis is distance D(m) from the end of the guideshaft 322B. As the magnet 330 is fixed to the end of the guide shaft322B, and the steel plate 329 is fixed to the guide member 322A, thethrust of the linear motors 323A, 324A and 323B, 324B required for thestill-positioning of the wafer table 320 at the end of the guide shaft322B can be reduced and the heating amount can be controlled.

[0169] Next, the structure of the support legs 331A-331C that supportthe wafer table 320 with respect to the wafer base 307 of the exposureapparatus of this example is explained.

[0170]FIG. 25A is an enlarged view showing the support leg 331A and thelike of the wafer table 320. FIG. 25B is a side view. In the support leg331A, between slot 331Aa and a lower slot 331Ab is a displacement part334. A fluid bearing 332A is attached to the bottom of the displacementpart 334 through a spherical bearing 335 so that it can be rotated. Inthe same manner, as shown in FIG. 13, fluid bearings 332B and 332C arefixed to the other support legs 331B and 331C. The fluid bearing 332A isdisposed on the wafer base 307 of FIG. 13 by a hydrostatic pressurefluid bearing method. Additionally, as shown by the support leg 331B ofFIG. 13C, piezoactuators 333 are fixed to the support legs 331A-331C,and the piezoactuators 333 are fixed to the wafer table 320 via fixingmembers 353.

[0171] Referring to FIGS. 25A-B, a displacement enlargement mechanismthat can be extended and retracted in the direction of support isstructured by the piezoactuator 333 and the displacement part 334. Thefluid bearing 332A has a magnet or a vacuum absorption part for applyingpressure. In general, because the displacement by the piezoactuator isonly approximately 60 μm, a displacement enlargement mechanism isneeded. The displacement enlargement mechanism of this example uses aparallel motion link. When the extending/retracting part of thepiezoactuator 333 presses an input point A of the slot 331Aa of thesupport leg 331A, the input point A is linearly displaced in thehorizontal direction by a minute displacement area. Then, point B of thelink mechanism part of the displacement part 334 of the displacementenlargement mechanism is rotated about center point C, and point D isdisplaced in a vertical direction as a result thereof. In thedisplacement part 334 of the displacement enlargement mechanism of thisexample, the slope of the link is 26.6°, the displacement enlargementpercentage becomes double, and it can be displaced to a maximum of 120μm. Furthermore, by adjusting the displacement of the displacement part334 of the support legs 331A-331C, correction of the tilt angle(leveling) of the wafer table 320 and the correction of the position inthe vertical direction (focus adjustment) with respect to the wafer base307 are performed.

[0172] Furthermore, even if the support legs 331A-331C are displaced 120μm, which is the maximum displacement amount, if focus adjustment andleveling cannot be appropriately performed, the front surfacepositioning of the wafer 303 is premeasured before the exposure starts,and the elevator driving part 308 of FIG. 11 is driven and the waferbase 307 is positioned so that the position of the surface of the wafer303 can be placed at a specified position (the image plane of theprojection optical system 302). After that, focus adjustment andleveling are performed by adjusting the support legs 331A-331C.

[0173]FIG. 26 is a block diagram showing a structure of a controllerthat controls the reticle stage 304 and the wafer stage 305. In FIG. 26,the main controller 350 supplies the desired value of the displacementamount to a desired position in the X and Y directions of the wafertable 320 of the wafer stage 305 and the Z direction of the support legs331A-331C to the subtractors 361 and 362, respectively. Based upon thevalue corresponding to a value that is multiplied by −¼ of the measuredvalue, from the desired position in the subtractor 361 of the laserinterferometers 318X and 318Y in the converter 365, the wafer stagecontroller 325 drives the wafer stage 305. The subtractor 362 adds avalue obtained by integrating the speed in the Z direction of the waferbase 307, which is measured by the speed sensor 336B, to the desiredvalue, and further supplies a value obtained by subtracting a defocusamount of the wafer stage 305, which is measured by an autofocus sensor,not depicted, to a support leg controller 363. The support legcontroller 363 controls the extending or retracting amount of thesupport legs 331A-331C, which support the wafer stage 305 based upon thesupplied value, and focus adjustment and leveling can be performed.Furthermore, the reticle stage controller 352 controls the reticle stage304, based upon the detection result of the vibration component (yawing)of the projection optical system 302 in the rotational direction aboutthe optical axis and the displacement of the wafer base 307 in thedirection perpendicular to the scanning direction detected by the speedsensor 336A, and on the value corresponding to the measured value of thelaser interferometers 318X and 318Y subtracted from the output of theconverter 365 using the subtractor 366. Thus, the effects of vibrationof the wafer base 307 in the horizontal direction can be reduced.Furthermore, the vibration of the wafer base 307 in the Z direction canbe reduced by a visco-elastic body 364.

[0174] Next, the wafer carrier mechanism of the exposure apparatus ofthis example is explained. In FIG. 11, in front of the wafer base 307, acarrier base 345 is disposed via a vibration control table 351. A wafercarrier mechanism such as wafer carrier arms 340A and 340B and the wafercassette 348 and/or the like are disposed on the carrier base 345.

[0175]FIG. 27A is a plan view showing part of the wafer carriermechanism of the exposure apparatus of this example. FIG. 27B is a sideview. First, the wafer stage 305 on which is disposed a wafer 303A towhich exposure has been completed moves from the exposure completionposition A to the wafer carrier position B, and the wafer 303A moves tothe position P1. At this time, three fingers of the wafer carrier arms340A are inserted into spaces which are surrounded by the wafer 303A andthe deep grooves 338 of the wafer table 320, and do not contact thewafer table 320. The wafer carrier arm 340A is attached on the supportpart 367A via an actuator 369A that can be extended and retracted in theZ direction and that can be rotated, and the support part 367A moves onthe carrier base 345 by a driving part 368A. A support part 367B, anactuator 369B, and a driving part (not depicted) are provided on anotherwafer carrier arm 340B as well. When the wafer stage 305 is still, thewafer table 320 releases the fixation of the wafer 303A by vacuumabsorption, and the wafer carrier arm 340A vacuum-absorbs the wafer 303Aand is raised by the actuator 369A. Furthermore, a wafer 303A to whichexposure has been completed is collected to the wafer cassette 348 shownin FIGS. 28A-B.

[0176] When the wafer carrier arm 340A raises, the wafer stage 305simultaneously moves at high speed to below the wafer carrier arm 340B(wafer carry-in position C) which holds a non-exposed wafer 303B. Whenthe wafer table 320 of the wafer stage stops, the wafer carrier arm 340Bis lowered by the actuator 369B, and the non-exposed wafer 303B isdisposed on the wafer table 320 and is vacuum-absorbed. At this time,because the wafer carrier arm 340B is also inserted into the deepgrooves 338, it does not contact the wafer table 320. After this, thewafer stage 305 moves at high speed from the wafer carrier-in position Cto the exposure start position D, the wafer 303B moves to the positionP2, and exposure begins. At the same time, the wafer carrier arm 340Btakes a new wafer out from the wafer cassette 348 of FIGS. 28A-B andwaits.

[0177] When superposition exposure is performed, the rotational angle ofthe wafer of the exposure object is measured in advance and the wafertable 320 is rotated during the positioning so as to cancel the angle ofthe wafer stage 305 at the wafer carrier position C. By doing this, whenthe wafer table 320 is facing in the scanning direction, a pattern thatis formed in a shooting area that is already arrayed in a grid state onthe wafer and a pattern image of the reticle 301 can be in a specifiedpositional relationship.

[0178]FIG. 28A is a plan view showing the vicinity of the wafer cassette348 when a wafer is carried out. FIG. 28B is a side view of FIG. 28A.The wafer carrier arms 340A and 340B can be freely driven in threedirections such as a rotational direction about the Z-axis, a scanningdirection (X direction), and a vertical direction (Z direction). A wafercassette support member 347 that supports the wafer cassette 348 on thecarrier base 345 can be freely driven in the vertical direction. When analready-exposed wafer 303A is collected to the wafer cassette 348,first, the wafer carrier arm 340A that holds the wafer 303A is revolvedby the actuator 369A. At the moment the wafer 303A goes through theposition P4 and reaches the front surface of the wafer cassette 348, thesupport member 367A of the wafer carrier arm 340A linearly moves to theposition P3 in the X-axis direction and the wafer carrier arm 340A isrevolved at the same time so that the wafer 303A linearly moves in theY-axis direction. Next, when the wafer 303A reaches a predeterminedposition within the wafer cassette 348, vacuum absorption by the wafercarrier arm 340A is released, and the wafer cassette support member 347raises and lifts up the wafer 303A. Then, the wafer carrier arm 340Aperforms an opposite operation compared to the previous process andwithdraws.

[0179]FIG. 29A is a plan view showing the vicinity of the wafer cassette348 when the wafer is carried in. FIG. 29B is a side view of FIG. 29A.When the wafer is carried out from the wafer cassette 348, first thewafer carrier arm 340B moves below the non-exposed wafer 303B. When thewafer carrier arm 340B stops, the wafer cassette support member 347lowers, and the wafer 303B is disposed on the wafer carrier arm 340B.Then, after the wafer carrier arm 340B vacuum-absorbs the wafer 303B,the support member 367B of the wafer carrier arm 340B linearly moves inthe X-axis direction, the wafer carrier arm 340B is revolved by theactuator 369B and takes the wafer 303B out from the wafer cassette 348.It then waits until the wafer stage 305 arrives. Furthermore, the wafercarrier arm 340B can linearly move parallel to the front surface of thedevice, so it is also possible to structure the device in-line withsurrounding devices such as a coater or a developer.

[0180] Thus, as the wafer stage 305 of FIG. 27 moves to the position ofcarrying out the wafer or the position of carrying in the wafer, it isnot necessary to temporarily fix and support the wafer as in aconventional exposure apparatus, and there is no need for receiving andgiving the wafer between wafer carrier arms. Therefore, the probabilityof foreign objects attaching to the wafer and the probability of carriererror can be reduced. Furthermore, a larger mass wafer can be carriedand a larger size of wafer can be developed, compared to when the waferis carried to the exposure position by wafer carrier arms, because theeffects of vibration of the wafer carrier arms are not easily receiveddue to the mass of the wafer.

[0181] While the present invention has been described with reference topreferred embodiments thereof, it is to be understood that the inventionis not limited to the disclosed embodiments or constructions. To thecontrary, the invention is intended to cover various modifications andequivalent arrangements. In addition, while the various elements of thedisclosed invention are shown in various combinations andconfigurations, which are exemplary, other combinations andconfigurations, including more, less or only a single element, are alsowithin the spirit and scope of the invention.

What is claimed is:
 1. A scanning exposure apparatus that exposes apattern of a mask onto an object, comprising: a mask stage that ismovable while holding the mask; a first electromagnetic driver having afirst portion coupled to the mask stage and a second portion to move themask stage in a scanning direction; a position detector having aninterferometer system that cooperates with a reflective portion of themask stage to detect a position of the mask stage, the reflectiveportion being positioned along the scanning direction; a counter weighthaving a bearing and at least one beam extending along the scanningdirection to move in a direction opposite to a movement direction of themask stage in response to a reaction force generated by a movement ofthe mask stage by the first electromagnetic driver, the counter weightbeing heavier than the mask stage, and a length of the at least one beamalong the scanning direction being longer than a length of thereflective portion along the scanning direction; and a projection systemthat projects the pattern onto the object, wherein at least a portion ofthe projection system is disposed vertically below the mask stage andthe counter weight.
 2. The scanning exposure apparatus of claim 1,wherein the second portion of the first electromagnetic driver iscoupled to the at least one beam.
 3. The scanning exposure apparatus ofclaim 2, wherein the counter weight is movably supported by a base viathe bearing.
 4. The scanning exposure apparatus of claim 3, wherein thebearing is a non-contact bearing.
 5. The scanning exposure apparatus ofclaim 3, wherein the base movably supports the mask stage.
 6. Thescanning exposure apparatus of claim 4, wherein the at least one beam ispart of a frame member having a rectangular shape.
 7. The scanningexposure apparatus of claim 4, wherein the counter weight has a frameshape.
 8. The scanning exposure apparatus of claim 4, wherein the firstelectromagnetic driver comprises a coil member and a magnet member. 9.The scanning exposure apparatus of claim 8, wherein the first portion ofthe first electromagnetic driver is the coil member and the secondportion of the first electromagnetic driver is the magnet member. 10.The scanning exposure apparatus of claim 4, further comprising: a secondelectromagnetic driver coupled at least partly to the mask stage to movethe mask stage in a non-scanning direction different from the scanningdirection.
 11. The scanning exposure apparatus of claim 10, wherein thesecond electromagnetic driver comprises a coil member and a magnetmember.
 12. The scanning exposure apparatus of claim 4, wherein thelength of the reflective portion along the scanning direction is longerthan a stroke of the mask stage along the scanning direction.
 13. Thescanning exposure apparatus of claim 1, wherein the at least one beam ispart of a frame member having a rectangular shape.
 14. The scanningexposure apparatus of claim 1, wherein the counter weight has a frameshape.
 15. The scanning exposure apparatus of claim 1, wherein the firstelectromagnetic driver comprises a coil member and a magnet member. 16.The scanning exposure apparatus of claim 15, wherein the first portionof the electromagnetic driver comprises the coil member and the secondportion of the electromagnetic driver comprises the magnet member. 17.The scanning exposure apparatus of claim 1, further comprising: a secondelectromagnetic driver coupled at least partly to the mask stage to movethe mask stage in a non-scanning direction different from the scanningdirection.
 18. The scanning exposure apparatus of claim 17, wherein thesecond electromagnetic driver comprises a coil member and a magnetmember.
 19. The scanning exposure apparatus of claim 1, wherein thelength of the reflective portion is longer than a stroke of the maskstage along the scanning direction.
 20. A scanning exposure apparatusthat exposes a pattern of a mask onto an object, comprising: movableholding means for holding the mask; moving means for moving the movableholding means in a scanning direction; position detecting means havingan interferometer system that cooperates with a reflective portion ofthe movable holding means to detect a position of the movable holdingmeans, the reflective portion being positioned along the scanningdirection; balancing means having a bearing member and a first memberextending along the scanning direction to move in a direction oppositeto a movement direction of the movable holding means in response to areaction force generated by a movement of the movable holding means bythe moving means, the balancing means being heavier than the movableholding means, and a length of the first member being longer than alength of the reflective portion; and projecting means for projectingthe pattern onto the object, wherein at least a portion of theprojecting means is disposed vertically below the movable holding meansand the balancing means.
 21. A scanning exposure apparatus that exposesa pattern of a mask onto an object, comprising: a projection systemdisposed between the mask and the object to project the pattern onto theobject; a mask stage that is movable while holding the mask; a firstelectromagnetic driver having a first portion coupled to the mask stageand a second portion to move the mask stage in a scanning direction; asecond electromagnetic driver coupled at least partly to the mask stageto move the mask stage in a non-scanning direction different from thescanning direction, a moving distance of the mask stage in thenon-scanning direction by the second electromagnetic driver beingshorter than a moving distance of the mask stage in the scanningdirection by the first electromagnetic driver; a position detectorhaving an interferometer system that cooperates with a reflectiveportion of the mask stage to detect a position of the mask stage, thereflective portion being positioned along the scanning direction; and acounter weight having a bearing and at least one beam extending alongthe scanning direction to move in a direction opposite to a movementdirection of the mask stage in response to a reaction force generated bya movement of the mask stage by the first electromagnetic driver, thecounter weight being heavier than the mask stage, and the at least onebeam being coupled to the second portion of the first electromagneticdriver.
 22. The scanning exposure apparatus of claim 21, wherein alength of the at least one beam along the scanning direction is longerthan a length of the reflective portion along the scanning direction.23. The scanning exposure apparatus of claim 22, wherein the length ofthe reflective portion along the scanning direction is longer than astroke of the mask stage along the scanning direction.
 24. The scanningexposure apparatus of claim 22, wherein the counter weight is movablysupported by a base via the bearing.
 25. The scanning exposure apparatusof claim 24, wherein the bearing is a non-contact bearing.
 26. Thescanning exposure apparatus of claim 24, wherein the base movablysupports the mask stage.
 27. The scanning exposure apparatus of claim25, wherein the second electromagnetic driver comprises a coil memberand a magnet member.
 28. The scanning exposure apparatus of claim 25,wherein the at least one beam is part of a frame member having arectangular shape.
 29. The scanning exposure apparatus of claim 25,wherein the counter weight has a frame shape.
 30. The scanning exposureapparatus of claim 25, wherein the first electromagnetic drivercomprises a coil member and a magnet member.
 31. The scanning exposureapparatus of claim 30, wherein the first portion of the electromagneticdriver comprises the coil member and the second portion of theelectromagnetic driver comprises the magnet member.
 32. The scanningexposure apparatus of claim 21, wherein the at least one beam is part ofa frame member having a rectangular shape.
 33. The scanning exposureapparatus of claim 21, wherein the counter weight has a frame shape. 34.The scanning exposure apparatus of claim 21, wherein the firstelectromagnetic driver comprises a coil member and a magnet member. 35.The scanning exposure apparatus of claim 34, wherein the first portionof the electromagnetic driver comprises the coil member and the secondportion of the electromagnetic driver comprises the magnet member. 36.The scanning exposure apparatus of claim 21, wherein the secondelectromagnetic driver comprises a coil member and a magnet member. 37.The scanning exposure apparatus of claim 21, wherein the length of thereflective portion is longer than a stroke of the mask stage along thescanning direction.
 38. A scanning exposure apparatus that exposes apattern of a mask onto an object, comprising: projection means forprojecting the pattern onto the object; movable holding means forholding the mask; first moving means for moving the movable holdingmeans in a scanning direction; second moving means for moving themovable holding means in a non-scanning direction different from thescanning direction, a moving distance of the movable holding means inthe non-scanning direction by the second moving means being shorter thana moving distance of the movable holding means in the scanning directionby the first moving means; position detecting means having aninterferometer system that cooperates with a reflective portion of themovable holding means to detect a position of the movable holding means,the reflective portion being positioned along the scanning direction;and balancing means having a bearing member and a first member extendingalong the scanning direction to move in a direction opposite to amovement direction of the movable holding means in response to areaction force generated by a movement of the movable holding means bythe first moving means, the balancing means being heavier than themovable holding means.
 39. A stage apparatus having a movable stage thatmoves in a scanning direction, the stage apparatus comprising: a firstelectromagnetic driver having a first portion coupled to the movablestage and a second portion to move the movable stage in the scanningdirection; a second electromagnetic driver coupled at least partly tothe movable stage to move the movable stage in a non-scanning directiondifferent from the scanning direction, a moving distance of the movablestage in the non-scanning direction by the second electromagnetic driverbeing shorter than a moving distance of the movable stage in thescanning direction by the first electromagnetic driver; a positiondetector having an interferometer system that cooperates with areflective portion of the movable stage to detect a position of themovable stage, the reflective portion being positioned along thescanning direction; and a counter weight having a bearing and at leastone beam extending along the scanning direction to move in a directionopposite to a movement direction of the movable stage in response to areaction force generated by a movement of the movable stage by the firstelectromagnetic driver, the counter weight being heavier than themovable stage, and the at least one beam being coupled to the secondportion of the first electromagnetic driver.
 40. The stage apparatus ofclaim 39, wherein a length of the at least one beam along the scanningdirection is longer than a length of the reflective portion along thescanning direction.
 41. The stage apparatus of claim 40, wherein thelength of the reflective portion along the scanning direction is longerthan a stroke of the mask stage along the scanning direction.
 42. Thestage apparatus of claim 40, wherein the counter weight is movablysupported by a base via the bearing.
 43. The stage apparatus of claim42, wherein the bearing is a non-contact bearing.
 44. The stageapparatus of claim 42, wherein the base movably supports the mask stage.45. The stage apparatus of claim 42, wherein the at least one beam ispart of a frame member having a rectangular shape.
 46. The stageapparatus of claim 42, wherein the counter weight has a frame shape. 47.The stage apparatus of claim 42, wherein the first electromagneticdriver comprises a coil member and a magnet member.
 48. The stageapparatus of claim 47, wherein the first portion of the firstelectromagnetic driver comprises the coil member and the second portionof the first electromagnetic driver comprises the magnet member.
 49. Thestage apparatus of claim 42, wherein the second electromagnetic drivercomprises a coil member and a magnet member.
 50. The stage apparatus ofclaim 39, wherein the second electromagnetic driver comprises a coilmember and a magnet member.
 51. The stage apparatus of claim 39, whereinthe at least one beam is part of a frame member having a rectangularshape.
 52. The stage apparatus of claim 39, wherein the counter weighthas a frame shape.
 53. The stage apparatus of claim 39, wherein thefirst electromagnetic driver comprises a coil member and a magnetmember.
 54. The stage apparatus of claim 53, wherein the first portionof the first electromagnetic driver comprises the coil member and thesecond portion of the first electromagnetic driver comprises the magnetmember.
 55. The stage apparatus of claim 39, wherein the length of thereflective portion along the scanning direction is longer than a strokeof the mask stage along the scanning direction.
 56. A stage apparatushaving a movable stage that moves in a scanning direction, the stageapparatus comprising: first moving means for moving the movable stage inthe scanning direction; second moving means for moving the movable stagein a non-scanning direction different from the scanning direction, amoving distance of the movable stage in the non-scanning direction bythe second moving means being shorter than a moving distance of themovable stage in the scanning direction by the first moving means;position detecting means having an interferometer system that cooperateswith a reflective portion of the movable stage to detect a position ofthe movable stage, the reflective portion being positioned along thescanning direction; and balancing means having a bearing member and afirst member extending along the scanning direction to move in adirection opposite to a movement direction of the movable stage inresponse to a reaction force generated by a movement of the movablestage by the first moving means, the balancing means being heavier thanthe movable stage.